Pain After Anal—Help please!

So my FWB and I tried anal last night. It was my first time trying it, and after 3 pumps I told him to stop because it was hurting too much. He stopped, and we kept having sex, which was amazing as always. Anywho, now it's the morning after, and my ass hurts a lot.

Any advice on how to relieve some of the pain would be greatly appreciated:)