After finishing a round of antibiotics and a shot to get rid of my abscessed tooth i now have a knot in the center of my left jawline, what is it?

Swollen Glands: When you get infection inside the mouth like tooth in your case, it can cause swelling of the lymph glands, and your tooth infection caused the swelling in lymph glands in left jawline.Even when the infection clears up the gland may remain enlarged for a while but if it persists or gets bigger, get it checked by your doctor.

Could be infection: Antibiotics rarely, if ever, are a solution for abscessed teeth. The medicine can relieve pain for a short time, but the problem will persist until the tooth is treated by root canal therapy or extraction. The reason is the lack of healthy blood supply inside the tooth itself. Without in tact and healthy blood vessels, the antibitocs never reach the source of the injection. See an endodontis.