I am not a veterinarian, but without the aid of veterinary services I don't think that this is something that can be "fixed" by the average poultry keeper.
I would suggest culling the chick, it will die when it either starves or is trampled or killed by the bigger stronger chicks. It's hard to do, but sometimes it's the best thing.
Has it been like that since it hatched? Day 1 it might have been helped, the older it gets the harder it gets as they grow so fast.