So you used a big dildo, and ended up with a prolapsed anus. You've probably bruised your anal spincters, possibly even torn them by inserting the dildo too forcefully. I am not an MD, but here's what I suggest: take ibuprofen, then sit in a warm (not hot) bath, and when things relax, using plenty of lube, push the prolapse back inside. You might find using a dildo (not the monster you've injured yourself with) will help push the prolapse back inside. I suggest a soft diet for a week so you can take a dump without straining.
But you'd be far better off getting medical care in case you've done more than just bruise yourself.
I suspect you were high as a kite (on meth, perhaps?) and sat down on the thing forcefully. (Or did you hookup with some rough tough ignoramus of a wannabe top and he did it?) That's a really good way to injure yourself, as you are finding out. You need to give up the drugs (if any), and find a boyfriend experienced at anal play to give you what you want without force or violence. Assholes are very important organs and deserve to be treated with respect, not physical abuse. Remember, lots of guys can take an entire hand and not suffer injury.