i assume it pipped at the small end, right?
Just keep a close eye on it. I have had it happen before and they were fine but sometimes they can get this gooey, sticky stuff on them (maybe yolk?) and it gets them stuck or can drown them. help it if it really looks like it needs it but if it seems to be doing okay i would let it go by itself.
I sometimes had to GENTLY peel some of the shell off to be able to see better and make sure it was making progress. Peeping at them always helps too, it's like the momma talking to them. I noticed when i peeped at my last batch they came out a LOT faster then the ones before them that i left alone.
I have had a few pip the wrong end too - some I have has to help- but some have made it out on their own. I have found they can take a little longer than the other to hatch as they dont have as much room inside the egg to move around.
Hope the little one still makes it out ok for you!