Accidental Anal - TMI OUCH

So I was having sex with my boyfriend in the shower tonight and he was in me from behind. Anyway because it's the shower it's slippery and he slipped out straight into my asshole.. His dick is maybe 8-9 inches when hard and very wide and it hurt me so badly, the pain was so bad I almost passed out. Anyway it's been 8 hours and my ass hole is still really sore and I had the tiniest little bit of blood straight after but that's stopped now. 
Should I worry about this pain? What could it be from? 
Ps yes he definitely did it on accident. We were having very rough sex in the shower and it was very slipper with the soap and he slipped in, I felt it. Then he cried when he saw me in a lot of pain ha.