Speaking from experience... he doesn't know if he can argue with that, and he is frankly a bit shocked to hear it, but that doesn't stop the knee-jerk feeling that he needs to be at least a bit defensive about this.

"I think I'd know if I'd fractured something." But, like, would he? Would he really? For a moment after he stands, he does seem fairly unsteady, but finds his balance quickly enough. All he has to do is keep his mind off of it, and narrow his focus on to literally anything else, easy as that.