HELP! My budgie's leg might be broken?!?

I'm not sure if it is broken or sprained but I got home from school today and noticed he was hopping around on 1 leg and and holding up his other one. I gently moved the leg around and was stroking it for him and he didn't seem to be in ANY pain or discomfort, so what is wrong with it? Does anybody know? Is there anything I can do to ist with the healing or will he always have to hop around? I feel so terrible!!!!