Thanks very much.
If he is weight bearing at all then a fracture is much less likely. And the fact that he can get up and down, even though he may be struggling, and is willing to eat and drink are all good signs as well.
But that doesn't mean that he isn't hurting. Soft tissue injuries can be quite uncomfortable too.
He may be holding his leg at a different angle in an attempt to avoid putting pressure on it. When I asked about angulation I meant a sharp change in position/bend compared to his other leg (which would indicate a fracture that didn't break the skin).
So at this point I would be concerned about a soft tissue strain to one of his joints or that he managed to wrench his neck when he stumbled such that the nerve roots to that leg were stretched and are causing him pain.
I don't think that he needs emergency treatment today necessarily.
I would make him rest as much as possible. The more he moves around the greater chance he has of injuring himself further or hurting another leg trying to take weight off his sore one.
He should be carried in and outside, and leash walked to eliminate to keep him from being overactive. Indoors he should be closely confined to one room. No stairs or jumping.
I would elevate his food and water bowls to head height so he doesn't have to bend.
If you can find the sore spot icing it with cold packs for 10 minutes at a time several times today should help.
Then if he isn't much better by morning have him examined by his veterinarian.
I do not recommend giving him any over the counter medication because that will interfere with more effective medications that your veterinarian can prescribe tomorrow, and we want to see what rest alone does for him overnight.
Best of luck with your fellow, please let me know if you have any further questions.