I think my external hemorrhoid ruptured. it looks black and blood consistently coming out. looks like open wound. how long before its stops bleeding?

Few days: Sound like you had a thrombosed external hemorrhoid. Once ruptured the pain should have felt better. Bleeding should stop within a few days but i would see a physician to give better advice and follow this up.

Care of hemorrhoids: I agree about likely rupture. Hemorrhoids are a dilation and swelling of the expandable tissue around the rectal opening. Non operative treatment includes a bowel regimen (fiber, stool softeners, laxatives to goal of 2 soft bowel movements daily) local salves (prep h, desitin, (zinc oxide diaper cream) anti fungals, ) and hygiene (shower, hair dryerdryer daily). Surgery when above fails. Ok to see doc.