I've posted my abscess story before so I won't bore anyone with the details again. Bottom line, Eva Lou is right about pain vs. burning but I'll add something else. If you run a fever, it could also be a sign that there's an abscess. That's what finally sent me to the hospital. Even an experienced gastro doc sometimes can't tell in the office if it's an abscess because the swelling and redness can duplicate the symptoms of a fissure. I needed an MRI for them to find my abscess. Go back to your doctor if your symptoms aren't improving. An abscess that bursts on its own can cause a fistula (like Eva Lou said) or can get into your bloodstream and give you a potentially deadly infection.
My pain was so bad I couldn't stand under my own power. It hurt worse than breaking my arm, tearing my knee, and popping my hamstring (done all three). If the pain is incapacitating and constant, and not reacting to cortisone suppositories and epsom baths, it's probably not a fissure.
Keep us updated and fell better.