What could it be if there’s a hard lump inside the anus, no bleeding, but pain is present?

A hard mass inside the anus—without rectal bleeding but accompanied by pain—may indicate a submucosal abscess of the rectum. This can occur when an anal gland becomes infected and the infection spreads along the anal canal and rectum into the surrounding tissues, resulting in a submucosal rectal abscess. Such a mass is typically detected during digital rectal examination. In most cases, definitive diagnosis can be achieved using perianal ultrasound or endorectal ultrasonography. If the lesion is a rectal polyp or rectal adenoma, it usually exhibits good mobility and does not invade the submucosal blood vessels of the rectum; therefore, it generally does not cause rectal bleeding. However, localized inflammation of a polyp or adenoma may lead to pain.