Something else to consider, since you're imagining theoretical events. If the dog's collision with the wall was so forceful that it broke bones in the dog's muzzle, the resulting displacement of bone and tissue could have the appearance of "puffing" or "fattening up" the shape of the dog's head. Particularly if bones were displaced, meaning that the ends were pushed apart and out of line with each other instead of merely cracking or breaking but maintaining alignment, the shape of the head could be significantly altered as a result of the crash into the wall.

I'm not sure a collision with that much force would ever happen in real life, but this could be another result if it did happen!