I don't remember if Bran from Game of Thrones reveals to anyone that Jaime threw him from the top of the castle or what he saw on that day to anyone after he gets conscious. Does anyone know why? Is he keeping a secret? Is he scared of anything/anyone?
Bran seems to be unable to remember the events prior to the fall.
Tyrion asked him about it on his travels back from the wall.
(Tyrion) "Tell me, how is it you happened to fall that day?"
"I never," Bran insisted. He never fell, never, never never.
"The child does not remember anything of the fall, or the climb that came before it," said Maester Luwin gently. - A Game of Thrones: Chapter 24, Bran IV
During his coma he does recall some of it, but the Three-Eyed Raven tells him it is not important:
Bran was staring at his arms, his legs. He was so skinny, just skin stretched taut over bones. Had he always been so thin? He tried to remember. A face swam up at him out of the grey mist, shining with light, golden. "The things I do for love," it said. Bran screamed.
The crow took to the air, cawing, Not that, it shrieked at him. Forget that, you do not need it now, put it aside, put it away. It landed on Bran's shoulder, and pecked at him, and the shining golden face was gone. - A Game of Thrones: Chapter 17, Bran III
Also, bit later Bran is having dream about climbing;
... He forced himself to climb faster. The gargoyles watched him ascend. Their eyes glowed red as hot as coals in a brazier. Perhaps they had once been lions, but now they were twisted and grotesque. Bran could hear whispering to each other in soft stone voices terrible to hear. He must not listen, he told himself, he must not hear, so long as he did not hear them he was safe. But when the gargoyles pulled themselves loose from the stone and padded down the side of the tower to where Bran clung, he knew he was not safe after all. - A Game of Thrones: Chapter 17, Bran III
This trend continues as Bran tries to come to grips with his new restrictions,
Bran did not remember falling, yet they said he has, so he supposed it must be true. He had almost died. When he saw the weather-worn gargoyles atop the First Keep, where it had happened, he got a queer tight feeling in his belly.- A Clash of Kings, Chapter 4
The memory shows up again in his dreams with the three-eyed raven; although Bran does not remember who or what it is:
A golden man appeared in the sky above him and pulled him up. "The things I do for love," he murmured softly as he tossed him out kicking into empty air. - A Clash of Kings, Chapter 16
The incidents with the Three-Eyed Raven show us that Bran has repressed the memory or the Three-Eyed Raven has removed it via magic. The dreams show there is probably still a seed of the memory although Bran can not fully recall it. Given that these chapters are from Bran's POV, if he did remember, he could have told us as readers but not the spoken the words to anyone in-universe.
Although these passages are from the books, I feel they are relevant because Season 1 and 2 of Game of Thrones TV show was highly faithful to source material. As it is harder to convey the inner workings of a human mind on screen than on paper, the fact must confirmed a different way.
The scene in Winterfell plays out almost as exactly as it does in the books.
However, there is scene in the show that is not in the books where Robb asks Bran about the fall. This gives the never angle and also reinforces that Brann does not remember anything.
According to the linked Game of Thrones Wikia article, Bran was left comatose after he was pushed from the tower.
Bran awakens with no memory of what happened some weeks later, at the same moment as his father is forced to kill Sansa's direwolf, Lady.
Throughout the entire seasons up to Season 6, there has been no scene showing Bran recovers his lost memory. I am not sure whether he will be able to know who pushed him through warging in the remaining seasons.
Bran's character does not look at the Why of things, he is looking at What Is...the practical side. As he is recovering from the over all shock to his body, who would he tell? His parents have left for the south and the household is thrust into the chaos of his Father's situation. From the author's perspective it would not move the plot along to have him dwell on "Who did this?" because the audience/readers already know.
The "accident" helps reveal character of Jaime & Cersei, and lengths they will go to out of their loyalty to one another. The accident is also the vehicle that moves Bran into his new dimension and growth under guidance from the Three Eyed Raven. Bran is in a new state of confusion that continues to see things differently, little by little moving toward a state of clarity.
I think a good extension of this is to consider how far his new ability will be able to influence the Future...Raven tells Bran "The Past is already written. The ink is dry." Many explore the idea this is Time Travel but it is more of the Author's vehicle to gradually reveal information and add to our suspense and interest to see what will happen next.