Jaw pain on one side can be caused by a number of different things, including trauma to the jaw, temporomandibular joint disorder (TMJD), grinding the teeth, or other dental issues such as cavities or damage to the teeth, among others. Pain can present on one or both sides of the jaw, and just because it starts on one side doesn't mean it won't migrate to the other. Persistent jaw pain should be addressed by a dentist, who ideally will be able to determine the cause of the pain and take steps to correct it.
Regularly clenching the jaw or grinding the teeth at night is one of the most common causes of jaw pain on one side. This can also cause damage to the teeth, which can worsen the pain as well. Practicing stress reduction techniques and wearing a mouth guard at night can help to prevent the jaw clenching and grinding that leads to pain. TMJD is an actual medical condition that causes inflammation of the joints in the jaw; though this usually causes pain on both sides, not just one, it is something to consider if the jaw pain does not resolve within a few days.
Issues with the teeth are also very likely to cause jaw pain on one side. Cavities and infected teeth in particular can be very painful, and the pain can migrate down into the jaw bone. Teeth with damaged nerves can also cause sharp, persistent pain in the jaw, and it can be difficult to tell if the pain is originating in a tooth or the jawbone itself. Wisdom teeth that are growing improperly and potentially becoming impacted underneath or behind other teeth can also be very painful, and have the potential to push other teeth out of alignment.
An abscess or infection in the mouth, or a growth, can cause jaw pain on one side and should also immediately be checked out by a dentist for treatment. Another potential issue to keep in mind is that the sinuses are located in the cheekbones, and sometimes an infection or issue with the sinuses can cause pain in the jaw. Ear infections can also present as pain in one side of the face and the upper jaw. Even something simple like muscle tightness in the neck and shoulders, or chewing foods that are too tough, can lead to this type of pain.