Texas Diamondback won't close his mouth

by Chelsea
(Los Angeles, CA)

I have a Texas Diamondback Terrapin and he's about three years old. When we first got him, his mouth closed completely, but about a month or so ago there seemed to be a small gap (kind of like a hole) in his beak. I thought it might have been a crack, but he wasn't acting sick so I didn't think much more of it. Now his mouth is open all the time (just slightly, but enough for me to see inside his mouth), except for when he's sleeping, so I'm worried he may have injured his mouth biting hard things (he likes to bite his filter, his food container... pretty much anything he can "play" with). I read about RI, and there's no puss or foam coming from his mouth, he's eating consistently, and his stools look normal, so I don't think that's it. He's swimming, playing, and hibernating/sleeping like normal, but that consistently open mouth has begun to worry me. The inside is pink, like normal, but it may be a little puffy, I'm not sure.

If this is nothing, I'd love to hear it so I can stop worrying. I'm a first time turtle mom, so I worry about everything, but I'd rather ask and have it turn out to be nothing than to do nothing and have it get worse. :(

Thanks so much for any help you can give!