Bill, I have some trismus, which is worse on some days than others. I also concur that yawning is a really bad idea. Besides the jaw, my neck really goes nuts when I yawn.

Is the trismus a sharp pain? Yes and no. On the one hand, it is not like the pain of breaking a bone, but it is more acute than an ache. I would describe it as a sort of burning\cramping type of sensation.

A couple of things that I do to help it. One is jaw exercises --just repeatedly opening, closing, and moving side to side. The second is making sure that my neck and shoulder muscles are as loose as possible. Difficult for me right now, due to aftereffects of bilateral neck dissection, and some residual from my cervical fusion, but when my neck and shoulders are looser, the jaw muscles also do not work as hard.

Hope you are feeling better soon.