How old is it? It could be straddle/splay leg, in which case you will need to use something to attach the legs together. Some people use band-aids, while others use tape or a loosely tied rubber band. Others put the chick in a small glass or cup so that it can't lay down. They feed/water the chick regularly, and the standing straight up strengthens the legs into the right position.
Another possibility is slipped tendon. Unfortunately, I don't know enough about that to help you in treating it, but I think hat it involves pushing the tendon back into place and wrapping the leg so it stays there.
it hatched yesterday…. She seems very tired and just falls over. I made a rubber band/ hairband brace…. I hope this helps… it is both legs.. she is under a broody… can she stay under the broody? I gave her some more water.. he drinks with her eyes closes… Maybe she is just very tired??
I'm sorry for not responding earlier--is the chick still alive? The rubber band/hairband brace should help at least a little, but it is possible that the chick has something else wrong with it. The tiredness could be simply because it recently hatched, or due to an internal problem.