A common explanation for a toothache that's felt in the jaw is gingivitis and other gum infections. Rarely, a bone or sinus infection causes jaw pain.
Another cause of a "toothache" that is actually from jaw trouble is temporomandibular joint (TMJ) syndrome. This is a condition in which the TMJ is painful due to arthritis, a torn piece of cartilage, or other mechanical problems in the joint.
TMJ syndrome is especially likely if you have pain at the angle of the jaw (near the ear) with opening or closing of the jaw, a popping or clicking when you move your jaw, or if you grind your teeth when you sleep.
With your jaw pain, is there redness and/or swelling along the gum?