In the shower, i put a finger in my rectum for the 1st time. about 1in up, i felt something rough and sharp. no pain, no blood. i'm scared it's cancer?

May be tumor: Within 1 cm. of anal canal, the most common palpable lesion is a thrombosed hemorrhoid. At the same time one must be able to r.o. a malignant tumor such as squamous Ca or even an adenoCa. Mets can rarely be found there. While tumors can be rough, sharp is not a typical description unless there is something swallowed that impacts into anal canal. Bx underanoscopy needed.