My mouse also fell from the third floor. At that time, he was dizzy and dying, which was really pitiful ... but he survived because of the careful care of my family and me. His leg is broken, too. Feed him some nutritious food, let him recover naturally and let the hamster run a few steps slowly.
Maybe my injury is not as serious as yours, but just give you some advice. My hamster will recover soon, but it will recover slowly and naturally.