Congrats on the babies! If it were me, I may let nature take its course or put it down... that could potentially cause some serious issues down the road.... the old me would have done everything in my power to save it but even after all of my attempts nature won in the end in my experiences... I would maybe consult a vet on the best options for the little one.
It appears (photo not extremely clear) to be wht is called a "wry mouth". Sometime it can be corrected while the bones are still soft in the first day or two of life by actually manipulating it into correct position several times a day. I have seen 2 mini horses with such, presented on a forum for advice, and this is what was offered. One did this & bandaged it a couple hrs a day like you would a soft splint, it did straighten to 95%. Owner kept it and it did fine.
It could be a cleft deformity, also. A vet could tell with a visual.
Sometimes in utero they are squished and come out crooked.
Alright I'll message my vet a pic. He typically only does castration and sells dewormer but I'm hoping he can give me some answers. It seems to nurse off and on. It's not the best but it's not not nursing