Several things. This is a problem that requires a face-to-face meeting with your doctor. In that meeting, your doctor will listen to you, perform a throrough examination and possibly order labs or other tests. Based on this information, he/she will be able to tell you what's wrong and what to do about it.
Possible TMJ. See your dentist to be checked for TMJ.
See Your Dentist. What you are describing sounds like either an infection or trauma to your tempero-mandibular-joint (tmj). If you have been in an accident, or had trauma (a left hook?) to your jaw, your TMJ would have moved out of its socket. See your dentist or a TMJ specialist. This also could be caused if you grind/clench your teeth which would change your jaw's vertical dimension. A night guard may be needed.
Tender TM joint. You may have inflamed temporo mandibular joint. Avoid hard foods and take some nsaids. By the way how long you have this and what started the pain?
Possible TMJ. Inflammation of the TM joint will have pain when the jaw moves. Your pain may be from that or sinus or ear inflammation. Your dentist will be able to diagnose and treat or refer to the correct specialist.