anal sex

So last night my boyfriend was playing around and was like I'm gonna put my dick in ur butt and whatever and I was just like okay joking with him and then we were having sex and he said he actually wanted to try t and I was like sure I thought it wouldn't be hot but it hurt so bad and we couldn't even get it in so we had to stop but I wanna try again tonight bc I really want to do it with him. Any advice?