Did my dog break his leg?

Yesterday my dog tumbled down my deck stairs. When I looked down at him he was holding his front left leg in the air and whimpering. I couldn't take him to the vet last night but I am taking him to the vet today. This morning he still won't walk on it. If you gently touch it he doesn't do anything but if you move it around a little bit he tries to bite you and he starts to whimper. I am going to the vet but I want to know if you may know what's wrong.