Ouch.
I do tend to brux - there are a lot of contributing factors. Stress is definitely in there, my weird bite is part of it, and a lot of it is also the muscles of the neck that interact with the chewing muscles. I'd be surprised if your neck injury didn't contribute to it. Maybe your dentist can refer you to a massage therapist who works inside the mouth. Or you can poke around the insides of your jaw muscles with your own index finger for trigger points, as my LMT taught me to do. It's pretty painful, but worth it.