The best way to tell if your jaw is broken is to go in to the emergency room for an X-Ray. Short of that, a simple at-home test would be to bite down and see if you feel your bite is misaligned or if you feel there is something between your teeth preventing you from biting down fully. The nerve endings in your teeth are very sensitive to slight shifts in the boney architecture of your mouth. Therefore, if you feel your bite is misaligned or there is something between your teeth preventing you from biting down fully, there is likely damage to your jaw and/or teeth and an evaluation by a physician would become necessary.