I have just experienced the most amount of pain i probably ever had. I was yawning when suddenly my chin felt like someone wacked me with a brick round the face. My eyes just started watering and i had to get up and walk around... Thank god it only lasted for 10 seconds or so. Does anyone ever get that? It happened to me before just not as bad... lol chin cramp...
I've had it myself, usually when I've stared at a computer monitor to much then stretch. Sometimes it's the jaw, sometimes the back, etc Probally just a sign than I'm getting to fricken old.
I've gotten that a time or two.. Usually when yawning, like you. I get it under the chin, though. My jaw clamps shut and I stomp around the room waiting for it to go away.