This is an anal fissure.

It will be painful in the anal area if you have a fissure (tear). It should be looked at by your doctor.

Injection of botulinum toxin into the anal sphincter will cure up a fissure

An anal fissure is basically a tear in the anal area which is very painful and can be a cause for various infections.

An anal fissure is a tear in the anus. Painful bowel movements, constipation, and fecal impaction are all symptoms of anal fissures. One can also experience itching and bleeding in small amounts from the anus.