Hi Potato. I'm sorry your parakeet is hurt. I've had several birds, and I know how sweet they are.
You MUST get your bird to the vet. It's possible that a bone is broken or joint is damaged. Attempting a home remedy could do further damage. Allowing the bone to heal while misaligned could cause permanent lameness. Could it be infected? Only the vet can diagnose and treat the injury. I'm afraid that this is beyond home care. Please call the vet quickly.
Good luck to you and your feathered friend.
http://www.drsfostersmith.com/Articles/bird_commoninjuries.cfm
