Hello!
With him being as old as he is, it is probably a brake or arthritis. If you think it is a bite, check the area for a welt or bite area.
Either way if it is a bite or brake, try putting some ice on it, as this will help reduce the swelling.
If it is still swollen in the morning, he needs to be seen. If he is showing signs of an allergic reaction, (lethargy, excessive vomiting, blood in vomit or stool, labored breathing, ect.) he should be seen tonight.
If he's fine and just in a little pain, he will be fine until morning.
If there is anything else I can help you with, please let me know. If you feel I've answered your question, please, don't forget to click "Accept". Bonuses are always welcomed!Take care!Michelle }}i{{
Dog Expert
Work in dog grooming, raised several dogs. If I don't have the answer, I'll find it!