The symptom you have described is typical of TMJ, or temporomandibular Joint disorder, more commonly known as TMJ. Often referred to by doctors as simply a sore jaw, TMJ is a problem with the joint that makes up the jaw. This is a classic ball and socket joint and it can get disturbed due to a variety of reasons. Sometimes, things as simple as chewing forcefully can cause a problem with the smooth functioning of the joint. This is the strongest joint in the body and is held together with a number of muscles. This is the reason that it can go out of whack quite easily and effectively. Even if a single muscle out of the bunch holding this joint in place gets stressed, this can result in a joint problem quite quickly. What is more, this may not be easily diagnosed or even taken care of, since it is hardly possible to stop using the jaw for any length of time, except when sleeping. The symptoms of TMJ can be anything from the exact pain you have described to a general irritation in the ear or even a shooting pain in the jaw while eating or talking. In some really bad cases, even the cheekbones are affected due to this. The basic reason is that there is a fundamental change in posture that can cause the bad stiffening of other surrounding muscles. If there is even the slightest pain, the entire lower part of the face will tend to become stiff and painful because of the way it is held stiffly and hard.
The unhappy part of this problem is that there is no real cure for the problem except for proper rest and relaxation of the muscle. If the jaw has become really stiff and it is causing problems with such simple things like eating or speaking, then it would become mandatory to seek medical help. There would be a pressing need for measures such as taking a steroid injection that will help to find relief from the pain – at least enough so that a person can start to relax the jaw a bit. Cold and hot compresses applied alternately will be of some use. If possible and do-able, apply ice packs to get rid of the worst of the pain. Witch hazel is the only thing that can be of some help in curing the problem to a certain degree.