Split bumhole? treatment? :(?

You are describing an fissure. These can be very painful and difficult to heal. The initial management is to apply GTN ointment, which reduces the pain, and to keep the stool extremely soft so that the does not need to stretch when your bowel opens. If this fails, dilatation is performed under general anaesthetic to temporarily loosen the sphincter and again allow easier page of stool. See your GP.