I have a mole on my left buttock (Photo)

This is difficult to answer without pictures. I recommend following up with your cosmetic dermatologist. Hyperpigmented scars can be improved with a combination of lasers, Aerolase, microneedling/prp, skin lightening, peels, and skin care. Sun protection is essential. See an expert. Best, Dr. Emer

Yes, go see a dermatologist or a plastic surgeon, you would likely need a biopsy and a complete skin examination. You should try to get the pathology report of the original lesion removed years ago. Wish you the best in your journey, Dr Leo Kim, Specialist Plastic Surgeon in Sydney

It will be more difficult to visualise a mole if it has been traumatised, but some characteristics should still be present. If you mole has changed at all (change in size, shape, diameter, pigment, ulceration bleeding) than have it checked out.