I felt a painful pop when chewing. Did I rupture a mouth muscle or is this a TMJ symptom?

A TMJ symptom. Painful popping noises in the jaw joint while chewing are a common manifestation of TMJ problems. It usually indicates a partially displaced TMJ disc inside the jaw joint. To my knowledge, you can't rupture a mouth muscle while chewing. If the painful popping continues, you may want to seek treatment to prevent the disc from becoming completely displaced which may lead to locking or arthritis.
Symptom. Joints should be quiet. Painful pops should be evaluated. Most likely some joint damage has occurred. The nose at be the head of he aw is moving onto and off of its disc. This derangement can be stabilized. Have it heckled out!
Have it checked. If this is the first time that you have experienced a painful pop, you may have been on the borderline of a TMJ problem for awhile. Have this checked even if you think it may be a one time occurrence. Prevention is the best remedy. Know what to do if this event happens again!
TMJ. TMJ symptom of displaced disk. See a TMJ expert. Any dentist can be a TMJ expert with the proper training and experience. Most commonly, oral surgeons, prosthodontists, and orofacial pain specialists. Ask your MD, your dentist and your dental society for referrals.