Well, it's normal to bleed if anal penetration is done incorrectly. Incorrectly means not using lube or not using enough lube, the receiving partner being insufficiently relaxed and/or aroused, and going to fast or too big.

Anal stimulation should not hurt and should not produce blood. Pain and bleeding are signs of trauma, and your body's way of telling you that something is wrong.

Fortunately, assuming that the trauma was not substantial, it should heal on its own. Acute anal tears, also known as fissures, should heal within 6 weeks.

To speed the healing process, make sure that you drink plenty of hydrating liquids (e.g., not caffeinated beverages) and eat a diet high in fiber (brans, whole grains, peas, beans, citrus, prunes or prune juice, fiber supplements, etc.). Also avoid skin irritants, like scented soaps or lotions. Do take a 10-15 minute bath in warm water with nothing added to the water 2-3 times a day, though.

If the bleeding continues or the tear does not heal on its own, I would strongly recommend consulting a doctor. The doctor may prescribe you a medicated ointment or other form of medication.

Also, I hope you never see this person again. Anyway who causes their partner to lose a significant amount of blood and apparently doesn't stick around to make sure they're okay is not someone you want in your life.