
Sorry, maybe ‘lump’ isn’t very correct for what I’ve got. Maybe it is a spot.
Cyst ?, granuloma ? , bug bite ? (Some last for months ).
If I had that I would go to a dermatologist.
If you have been out in the sun this could just be a mole that has formed. Usually if a spot on the skin doesn’t itch ,bleed, darken, or spread,especially in an irregular pattern then its benign. The only way to truly put your mind at rest is to show a doctor.