Thanks for your concerns. By the description and the painful symptoms, most likely this is an annal fissure, like a "cut" in the perianal area which is as you well know very sensitive. The most common aggravating factror for it is constipation
, and thus, basic treatment to help healing includes topical medication
for comfort such as Preparation H, plenty of fruits, vegetables, fluid and fiber in your diet, and avoid vigorous wiping.
Dr Brenes-Salazar MD
Mayo Clinic MN