X2I would agree a deformity of some sort. They have a soft pallet just like a person. Can you look in the chicks mouth and see anything?
I would say if it seems to breathe ok now it should be fine. I would keep an eye on it as it may be more susceptible to respiratory infections or injury but I think it wouldn’t know the difference. It’s always breathed that way.
Do not use her in a breeding program