This is called incarcerated hemorrhoid, and the hemorrhoid which prolapsed and stayed that way swelled up. When the swelling reaches the external hemorrhoids, it hurts very badly because there are nerves which sense pain in the external hemorrhoids. The swelling probably happened suddenly, but wasn't there prolapse of the anus when defecating before this?

Prolapse of the anus can be treated by just pushing it back with your fingers, but the swelling reaches the outside of the anus in incarcerated hemorrhoid, so even if you push it back in spite of the pain, it will come out again soon; you'll be better off leaving it alone.

Okay, I'll prescribe painkillers and ointment and...You want to have it cut immediately?

I don't reccomend it. When it is swelled up all around like this, too much will be cut off, and it may cause trouble later on, like anal stenosis when the wound heals. Plus, when the inflammation of the part that swelled up heals, a lot of it will still be usable.

The best way, I think, is to exicise as little as possible, after the inflammation ceases, the part that prolapsed.

Why don't you use painkillers and ointment for a week, and see how it'll go? It will probably hurt for a few days, so take a break from your work if you can; rest and take a bath, worm your anus. When you come see me after a week, the swelling will still be there, but most of the pain will be gone.

Take care!