Thumb in my butt

Honey
I let him put a thumb in my butt. I don't know how to feel. It didn't hurt but it felt like I was going to shit. So I had him take it out. He used lube so it didn't hurt. He said that it was "fun". What does that mean? Fun? I feel like there is a new level of comfortablity now between us because he has had a finger in my butt.