Yes, I have had an anal fissure and it was absolute agony. It used to wake me in the night and I would sit in a bowl of salt water, crying in pain, so you have my devout sympathy.
I was reluctant to go to the doctor, but had to in the end and she knew without asking what was wrong by the way I perched, gingerly, on the seat! She prescribed some special cream which really worked wonders, so I would definitely go and get it seen to as soon as possible.
Good luck and I really hope you will feel better soon. 