Alternating cold packs and hot packs will help. Also a soft diet. Don't chew gum. When yawning hold under your chin so that your mouth doesn't open too wide. Anti-inflammatories such as Aleve or ibuprophin will help. Good luck, glad you have appt..
Try holding your tongue between your top front and bottom front teeth. Try to focus on relaxing those cheek muscles. Try circular massage at jaw joint, face muscles and around the ear. You actually may want to go to an oral maxillofacial specialist if your dentist only offers you a soft plastic night guard or says he can't do much to help you. You will want a hard plastic, flat planed splint. This is the kind I have and was recommended for me. It is expensive, but I'd be miserable without it. I have a classic type two overbite and arthritis in both jaws. If you try ibuprofen, you have to do it cyclically for at least two weeks if you expect inflammation to go down. You should be under the watchful eye of an oral maxillofacial specialist so they can judge if you are having improvement.