Sounds like an anal fissure to me.....I've had a few and yes, there is excruciating pain...A couple of things I have tried in the past and have helped. Believe it or not, Tinactin (foot cream).....got that suggestion from someone else...and worked sometimes....if it heals cuts in feet...why not in but???
Also would get wheat germ capsules, poke it open and put oil on butt sore. (Do this anytime you use bathroom). Do a search under "fissures" on the internet......Also, sit in a bathtub with warm water for as long as possible, as many times as possible......this will go away. I know the pain.