Pastel the Rooster
Crossing the Road
This is good advice. I twice this! I would do what Egghead_Jr said!!!Pick him up and fully inspect the leg. I've had to set legs and splint up and it's not fun. It takes two people. Ensure it's not dislocated. If it's just bruised or sprained you should consider caging him. Get him out of the flock and confined to a cage. He will rest then and give it a chance to heal. In the flock dynamic birds don't show weakness and when the others see it will bully them. If you take it out of the flock it doesn't attempt to put on a tough face and can relax to recoup.
Now that it's dark it's a good time to go get to inspect and apply aid if needed. At least get him in a cage when it's easy to capture capture him at night.