I would imagine someone with a broken jaw wouldn't be able to wear a football helmet. The pressure from the helmet against the side of your head would certainly cause pressure and pain on your jaw, add in getting tackled?
If this is some stage to allow us to move on in the QB position, I would have suggested sticking with the high ankle sprain that was from this game, and have AM watch some YouTube videos from wrestling schools on how to sell an injury. Let him ride off into the sunset with his 14-32 overall record as a starting QB without looking like he got benched in his final two games.