Hi Kev,
I have had TMJ a couple of times in my life. I was having unilaeral jaw pain a few weeks ago for a few weeks but it went away. Never went to the doctor. I had it (with a diagnosis, but TMJ might be one of those somewhat catch all diagnoses, not sure) really bad when I was 18 and was having arthritis flares in a number of joints at the same time (one knee, both hios, back vertebrae, neck vertebrae, jaw). I probably have some sort of inflammatory arthritis (in addition(?) to the FAI that has wrecked my hips).
That being said I also just found out I had a cavity in that neighborhood, but the pain faded away before found out about that.
I guess my point is that I am not aware that the jaw could be caused by your hip, but I do think there is a possibility of an underlying inflammatory condition. Or it could be unrelated completely and coming off the panadol (a pain-killer, right? opiate?) is just exposing that you have something else going on.
Hope it fades (as mine did). Was tough to chew for a while there.
Mike