The Doctor's mind is briefly elsewhere as he ponders another way to get information he wants. He's not fully paying attention to what the kid is doing until it's too late. He starts to ask Will what he's trying to do-more out of curiosity than anything and the next thing he knows the child is flung backwards.

He feels his hearts skip a successive beat in his chest and dashes over to kneel by the boy. "That was... nasty. Are you alright?" He offers a hand out to help the boy to his feet. "What was that-what did you do?"