this can be due to any problem with the TMJ- temporomandibular joint (located just ahead of ear) which maintains opening and closing of the jaw, like disc deformity, bone resorption...
Next Steps
consult oral and maxillo facial surgeon for further advice and x ray or cbct scan of tmj IF needed.
Health Tips
avoid excessive mouth opening, support your jaw (at chin) by a hand while yawing, sneezing, coughing and laughing.