Pain on the left side of the jaw is a condition that can be attributed to TMJ disorder. Patients with TMJ disorder may experience pain in the temporomandibular joint, abnormal mouth opening movements, or popping sounds when opening the mouth. In this case, you should avoid chewing hard food and try not to open your mouth widely to protect the temporomandibular joint, and pay attention to protection against cold and warmth. If the pain is obvious, it can be treated with non-steroidal anti-inflammatory and analgesic drugs. Acupuncture and physical therapy can also be used to relieve the pain. This condition may also be caused by lymphadenitis of the jaw. Patients with acute lymphadenitis may also develop swollen lymph nodes with pain and symptoms of pain on the left side of the jaw. When this occurs, antibiotics need to be applied for anti-infective treatment.