Sore after anal play 😫

My bf and I bought a butt plug to help me get used to the feeling of anal. It's slightly less thick than his dick but pretty close. I put lube on it and tried putting it in yesterday, the first time it hurt/stung pretty bad but the second time it was fine and I put it all the way in!!!! The pointy end of it even hit a spot that felt really good. Anyway, I kept it in and then took it out with minimal pain, but now if I expand/contract my butt muscles (kinda like pushing it in, the opposite of pooping, if you know what I mean haha) it's pretty sore. What can I do about this and when should I try the butt plug again?