Rectal pain is unfortunately a common condition. Given its sensitive nature, people often defer seeking medical treatment, however it is important to see a medical professional. I would encourage you to see your primary care doctor
as there are serious conditions to rule out.
The first thing that needs to be ruled out is an infection around the anus or in the rectum. Anorectal abscess
is a common condition which involves a "ball" of bacteria forming. A pilonidal cyst is similar condition forming around the hair follicles. Tenderness with sitting or touching the area, warmth and tenderness are symptoms consistent with this. The only way this will heal is if this is surgically opened. Your doctor can see this quickly on exam.
The other common condition is an anal fissure. This is a small tear in the rectum. As the rectal muscle is stretched with every bowel movement, the tear cannot heal as it constantly is used. Pain with every bowel movement, classically described as if you were "pooping glass" is a symptom of this. Your doctor can help with medication to allow this to heal.
Anal or rectal cancer is a consideration--although this would be rare. Hemorrhoids
can also be painful--especially if they are "thrombosed" which means the skin losses blood supply. Skin conditions like dermatitis can also cause these problems.
I would recommend seeing a doctor. These conditions can often be treated. If left untreated, some of these conditions can cause serious harm. Good luck.