Cannot Clench Due To Jaw Tightness. Have History Of TMJ. What Can It Be?

Good Evening, I have had jaw tightess and discomfort for many months now, and have an overbite that I tend to clench. In the last month or two I have noticed a movable, painless lump in front of my left ear where the hinge to my jaw is. It is not visible, but I can move it with my finger . It feels like it is pea-sized or so, but upon further inspection seems to connect to the jaw muscle that extends downward toward my earlobe . When I open my mouth the lump disappears. If i hold both sides of my jaw at the same point (where the lump is on left, and where it would translate to on the right), there is a slight shift movement like pushing one side inward pushes the otherside outward, just so slightly. Any idea what this could be? I dont have a history of TMJ but have been clenching in the last year.