Walter was not playing Jesse, just Gus.
Walter's intent was not to manipulate Jesse, but to manipulate Gus and the bodyguard into an unguarded place. Poisoning Jesse's girlfriend's son causes stress to Jesse, who believed it was the ricin from the cigarette. This heightened his stress level so he could not perform the cooking duties for Gus. Walter was forcing Gus into a conversation, at the hospital, that started as a cook responsibility conversation with Jesse, but turned into a compassionate one, since Gus relieved Jesse from cooking to stay near the boy. Walter knew Gus' attitude was "family first"; so does the audience. Walt used the unguarded time to bomb the car, a plan which failed because Gus luckily evaded the explosion by walking away because he "sensed something".
The remainder of the "situation" which involved the FBI, was defused by Saul, and the eventual knowledge that ricin (which was never named, I believe) was not the cause. It had to be something else Walter created because ricin, if confirmed, would have had Jesse arrested, possibly as a terrorist, since ricin is so deadly. Hello Guantanamo!