There are several complications to anal sex:
Pain from hemorrhoids. Hemorrhoids can be fragile and prone to bleeding, although they don’t usually cause the kind of pain you’ve described. You can frequently feel a hemorrhoid as a swollen, tender lump in the anal area. You’ll often notice blood from a bleeding hemorrhoid on toilet paper after a bowel movement, or on the stool itself.
Pain and bleeding can also occur when there’s a small tear in the lining of the anus called an anal fissure. Even small fissures can be pretty painful because they often cause spasms of the opening of the anus. They heal slowly because they’re irritated repeatedly during bowel movements. With anal fissures, you may also see blood on toilet paper or on the stool itself.
A rare, but serious, complication after anal sex is a hole (perforation) in the colon. This dangerous problem requires hospitalization, surgery to repair the hole, and antibiotics to prevent infection. A colonic perforation will usually cause fever and severe pain and pressure in the abdomen. This condition requires immediate medical attention, either through your health care provider or your local hospital emergency department.
Sexually transmitted diseases can infect the anus in much the same way as vaginal intercouse.
My advice to you if you do not have fever and the pain is somewhat bearable, is to take an colic pain killer, a stool softner for a couple of days. If you do not improve then you will have to consult someone face to face and you may even need a scope exam. A surgeon would be best at evaluating this condition.