Hi, although you've sent a pretty good picture, it's a bit difficult to say for sure what it is based on the picture alone.
One possibility, especially if it has been there for years with no change, is of a 'mole' or naevus.
Assuming that it is a naevus, such lesions are harmless and represent only a cosmetic concern. They could be left alone or removed surgically in a minor procedure.
If you are concerned, and especially if you notice any growth of the lesion, you should arrange an appointment for a more thorough clinic consult to determine the nature of the spot.
