Its been quite long since I last watched the Chronicles of Narnia - The Lion, the Witch & the Wardrobe. A question popped into my head that does Digory know about this magical wardrobe which is present in his home?
Yes Digory Kirke know about Narnia (and must be about Wardrobe) but not clear in the film universe yet because they didn't adopted the rest of the novels yet.
His story got explored in sixth novel The Magician's Nephew, where he was the young protagonist:
Digory's apple restores his mother's health, and he and Polly remain lifelong friends. Uncle Andrew reforms and gives up magic, but still enjoys bragging about his adventures with the Witch. Digory plants the apple's core with Uncle Andrew's rings in the back yard of his aunt's home in London, and it grows into a large tree. Years later, Digory's family inherit a mansion in the country, and the apple tree blows down in a storm. Digory has its wood made into a wardrobe, setting up the events in The Lion, the Witch and the Wardrobe.
So he himself have a hand in creation of the Wardrobe but used other method for going to Narnia which is explained in the same Wikipedia link I provided above.
Note 1: The Magician's Nephew was 6th novel but chronologically it's first.
Note 2: They are going by the book release order for film adaptation and 4th book's adaption is still under production but no fix plans for future novels adaptation yet.