Hi. Is this on the top part of your finger? Melanin can form in a clump (melanin is what gives our skin color) and make a spot. The sun really aggravates it. https://health.clevelandclinic.org/think-beauty-spots-arent-cute-heres/ Is it on the underside? It really is probably harmless either way. However, you should go ahead and get it checked out by a dermatologist. Melanoma typically is found on the torso and lower extremities but 'can' show on the palms of hands and soles of feet. https://www.cedars-sinai.org/health-library/diseases-and-conditions/m/melanoma-skin-cancer.html So, i just think it is in your best interest to get it checked out.