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 one hand and uncurl each toe one at a time until the toe is straight. In this position, massage the toe for 30 seconds and move to the next. Don't forget the thumb! If you have the boot on stretching the toes won't be necessary.
In any case, extend the leg completely until it is straight, and then fold it up until it's against the chick's body. Repeat this 20-30 times. Do this at least twice a day, and if it seems like it's not easy to bend don't force it, just fold it as far as it goes without much resistance.
Normal growth should help the chick's leg to revert to natural position, and if not, he will be fine! Just like human babies, some chicks are born with little hinderances like this, and he should learn to get along fine without pain or suffering!