You might be suffering from fissure in ano. It usually happens when people have constipation and strain during defecation. You will need to be examined per rectal by a general surgeon to identify the problem. In the mean time take plenty of water, high fibre diet, vegetables and some laxatives. Sitting in a tub of warm water will also help.

This can be anal bleeding or bleeding from rectum or colon....need to examine by procto scopy... If no bleeding from anal canal,,, then u may need to do colonoscopy