Jesus Christ!!! My mouse was eating his usual today, 2 fuzzies. while swallowing the last one I looked at him and oh my god!!

He has a slit, like half an inch long on his bottom jaw in the middle, I COULD SEE THE MOUSE HAIR THROUGH IT!!!!!

I feel terrible, he doesn't appear to be uncomfortable or anything but it is really scaring me if you can't tell.

Please somebody what do I do?