I did my first Master-Cleanse in February/March of this year, and I had serious jaw pain - I actually posted about it. It felt kind of like TMJ (I think, since I've never had it). I wasn't clenching, but I was feeling spasms. Also I had a sore spot on the underside of my chin. I tried to deal with it all by massage and meditation. It started around day 10 or 12 and ended sometime close to the end of my fast (I did 26 days).
In retrospect, I would say that this was a symptom of detox, but it might have been a parasite situation as well. I did use the Humaworm afterwards and had some interesting symptoms from that - namely amazing cramps in my legs and twitching at night.
Anyway, no worries in my opinion. Good job on making it through!