You'll need to take him in for an x ray to find out for sure. Just do your best to massage and stretch the toes for a few days to try and loosen them up. If they don't loosen even a little by day 4, it's probably a serious tissue deformity that can't be corrected with physical therapy. At that...
Probably a birth defect. The swelling means there is inflammation, but that can have a million causes. I have had a less severe form of this happen when one of my coturnix chicks hatched (assisted) two entire days late. He ran out of room and his leg and foot came out stuck in a curled up...
To me, it looks as if the bigger foot (his left, right side of the picture) is the normal one. The other one with crooked toes looks abnormal to me.
In addition to the boot, or even without it, it's important that you stretch those tendons to keep them from staying like that. Hold the chick in...