I bit down on a cookie and a sharp pain went from under my tongue on the right side up to my right ear and now there is a big swollen knot under my ja?

Try This: Sounds like a spasm of a jaw muscle. If it hasn't relaxed on its own try this: Make a fist with your right hand fingers pointing up and toward your face. Grasp your right wrist with your left hand. Place the fist under your jaw. Now while pressing upward, attempt to open your mouth against your fist. After a few moments see if the spasm has eased.if no improvement see your DDS.

Many possibilities: It's best to have your dentist take a look. A tooth may have cracked.