To overuse your jaw, softer foods, 600 mg of ibuprofen every 6 hours, heating pad on the cheek and massaging the muscles around the joint. If it progresses, seek a dentist.
Could be multiple possibilities. Dentistry is very hard to diagnose over the web. I could list multiple reasons, but it’s best to see your dentist. It could be an infected tooth. Tooth eruption depending on age or other factors.... Do you grind your teeth? Has there been any trauma? Etc. After you see your dentist, they will be able to take an X-ray or CT the area and do a physical diagnosis to see what the problem is.
Open wide and close into your normal bite several times. Is there pain, joint noise, other? Now do the same thing, except close so that you are closing with the biting edges of your front teeth touching. Is there any difference in comfort in the 2 jaw positions? If it is more comfortable in the “biting edge against biting edge,” see your dentist. Ask him to make an appliance designed to treat OSA for you. It will support your jaw more forward in the biting edge even with biting edge position. There will be a space between the teeth. They will not touch. This appliance is to treat your joints, not to treat OSA. Wear it all night every night. Allow your jaw 30 minutes to readjust after taking it out before trying to close your teeth together. Your chewing symptoms will decrease with time as your joints heal. You may get a better sleep as well. You may need additional treatment depending on results.
You should visit the dentist for orofacial pain.