You must have been carrying shark and none of that other stinky fish stuff
Well, other than the fact that it really pisses me off when I hear that thud, crunch or whatever other unpleasant sound it makes, it's not good for the helmet and you're really supposed to discard it after a fall on hard surface.
Of course, none of us do but it CAN affect the integrity of the helmet. Plus purdy helmets should be kept free from scratches