Have Cat Questions? Ask a Cat Vet Online.
Many cats will become agressive when they are in pain.
If he's still mobile and seems to be ok when you don't mess with him, you might be able to wait and see the vet tomorrow. If you are at all concerned, don't hesitate to give the vet a call and get some after hours advice.
Because the pain is around his bottom, it could be from an infected or overfull anal gland.
If this does not resolve itself, you will want to see the vet to have it checked.
Let me know if you still have questions.
Maybe.... It's really hard to say. The anal glands are at 10 and 2 beneath the tail.
If he's having trouble jumping, I would feel led to think that it is more of a back, hip or leg problem.
Until you can see the vet, I suggest that you limit his jumping by placing books or boxes at high objects so that he can climb up.