What is a lump under the jawline on your left side that is soft with a hard center and below it there is a double chin only on one side of your face?

I currently have a hard small lump under my jawline and i have been to numerous doctors and they have concluded that it is a deposit due to clenching your jaw at night. You will need to get a night guard and wear it at night. IF you do not the lump will continue to get more painful and you will start getting really bad headaches:(