Hello and welcome. As I read your questions it seems to me you are having unilateral masitric muscle hypertrophy.   It must be because of many reasons and most important one is, you must be chewing food only by same side because of the reason that your other jaw teeth either are not properly aligned or must be affected by some caries or other thing.    There are other possibilities like cystic lesion etc.  but these are rare.    You need to sort out the cause or if you feel more clarifications you can come back to me. Regards Dr Muzaffar