Irritation after anal sex

Hi there!

I had anal sex yesterday for the first time ever. Lube was used, as well as taking lots of time to stretch out. There was barely any thrusting it, it was pretty much put it in and see how it feels. It wasn’t painful either, it actually felt quite good! But today when I went to the bathroom (for a bowel movement..) afterwards my butt hole entrance was burning. Not super badly though. Would it just be irritation from something new going on there? Not enough lube? Any insights would definitely help 😊