Looks like the one side of the jaw is sunk in a bit. Same thing happened to me because I pulled the lower jaw up too tight to the upper jaw when I was putting it together. Fix it with your hair dryer after you get the inside resined and it's cured........I'm still trying to correct mine, only now I have to use Bondo to build it back out instead of fixing it when I was at the stage you're at. Don't make my mistake. Building out one area with Bondo means you also have to build out all the surrounding areas, just to keep everything even.....I had to adjust half the left side of the helmet just to fix the sunk in jaw/teeth area. Yours is looking good though....now I got to work on mine some more, lol.