a little over a month. It can take anywhere from a month to two months to heal. You have to give them a lot of TLC, but it is worth it. Since mine couldnt stand or walk, she would poop on herself so I would half to wash her butt everyday. They have this anti inflammatory mediecne that you can get at most vets. It is called mectan or mectam and it is almost $30. I didnt get any of it, because my SF leg wasnt swollen. I did give her 1/4 asprin, every couple days. I dont know if people really recommend that, but it didnt hurt her, I smashed it and mixed it with plain yogurt. Since your is a chick I probably wouldnt give it as much.
Now that I think about it your chick could have a calcium definacency (spelling?). I had a chick like that, but It hatched like that. so that might be what your has. But if that is the issue you can give it pol-vis-ol baby vitamins without iron. It is in like CVS and walgreens, it is $10-11. Just give it one drop 2-3 times a day.
Those are the only things I can think of.