When he flew and landed wrong, your rooster most likely sprained or pulled a tendon or ligament.
I've dealt with these types of injuries before and I can tell you that I've had good success with hens recovering from these injuries, but not so good with roosters.
These types of injuries take time to heal. He should be caged away from the flock and provided water and feed while caged. You can add vitamin B complex to his feed to eat. Crush a few tablets into powder and spread on top of his feed. The vitamin B complex might help speed up the healing process.
Keep him caged for 7 days, then remove him from the cage and see if there's improvement. If not, recage him for another 7 days and continue with the vitamin B complex in his feed. Take him out of the cage in another 7 days and see if there's improvement. If not, stop the vitamin B complex. Then you'll have some decisions to make. You can recage him until he heals, release him back with his hens, or cull him.
Caging birds with these types of injuries limits their movements as not to cause further injury, and giving time for it to heal properly. I've had birds caged anywhere from a couple of weeks to a few months before they healed and were able to walk and run normally, mostly all hens.
However with roosters, even caged with their hens around them, or caged away from their hens, are too anxious and skittish being separated away from their hens. Therefore their leg injury never heals properly or even worsens. I've had a couple of roosters over the years heal properly, but they reinjured their leg somehow and I eventually had to cull them or donate them to the feed store.
Remember, time heals.
