The usual cause of a sore jaw is grinding one’s teeth at night. Intense grinding can cause tempormandibular joint disorder (aka TMD) which can lead to splitting headaches. Usually these headaches cause pain that radiates from the front of your ears down to your lower jaw. So what is the solution? Try to relax before you go to sleep. Step aside 30 minutes to yourself to wind down before you go to bed. Meditate or listening to some relaxing music can help. Sleeping on your back can also help.