You need to consult the dentist. There are many causes of pain in lower jaw. Exactly cant say anything without proper examination. Meanwhile you can take painkiller like ketoroldt for temporary pain relief.

Hi,do warm salt rinses three to four times a day,avoid eating from affected side,consultation with a dentist in person is must.

Namaskaram, The condition which you are going through can be because of a impacted wisdom tooth . These teeth usually make a huge effort to erupt when they do have enough space . In this process there are a lot of changes that take place in the oral cavity like the gums near that perticular tooth get swollen , the adjacent tooth also is painful as it takes a lot pressure in this process . Sometimes due to lack of space these teeth get impacted in certain positions that may result in few unnecessary spaces where the food particles may get lodged resulting in infections . You do not deserve such pain and infection. Kindly visit a dentist who can examine your teeth clinically and take a couple of xrays to find out the real culprit behind your pain . Team Shambhala.