Hello dear, This sound is due to stetchining of muscle at jaw joint (known as TM joint). This usually happen during loude yawning or other activity which lead to excessive mouth opening. This disorder is known as MPDS in dentistry. In most cases it resolve in 3-4 days by doing following - - avoid mouth opening as far as possible - eat soft food - avoid eating on affected side - analgesic and muscle relaxant medication for relief of symptoms In extreme cases such yawning may lead to joint dislocation which causes excessive pain. But in your case there are least chance of dislocation. If your symptoms does not improve in next 2-3 days even after following above mentioned advise then you should consult dentist. I hove this will help you. My best regarda for early improvement.