I have a round dark purple vein above skin on inside butt cherk, 6in from anus.very painful to touch or sit. is it a hemorrhoid even if it's not on anus?

Not usually : This is very unlikely to be a hemorrhoid but does sound luje a thrombosed vein or varicosity. It could also be a pilonidal cyst that could benefit from lancing. Youse want to discuss with your internist.

May not be a vein.: This far from the anal opening it is definitely not a hemorrhoid, but could be any number of things that "look" like a bulging vein, like a cyst or fistula. Sounds as if this needs evaluation, since there are bowel conditions like crohn's disease that can present this way. See your doctor; if you want to use a specialist, consider a general surgeon or gastroenterologist.