I wish I could pinpoint the problem for you (or me!), but alas ... no.
While I've had tinnitus since '06, the jaw pain has only kicked in over the past 3 or so months when at the same time the tinnitus has blown me right off the charts.
I started to see a specialist just recently and he has asked me to do exercises to stretch the jaw - put left and right middle fingers on bottom teeth and left and right thumbs on upper teeth and press ... so that gently push your jaw into a more open position.
My problem is that this causes my daily headaches to be worse. However, I am told that if you don't have a headache probem, whis should potentially help.
Wishing you all the best.