Red spot with lump appeared on my lower leg. it turned black.test, no clot, no spider bite. lump still there and black after 1yr. size of a quarter

Bump on leg: It's hard to say for sure without seeing it and getting a better history, but any new unexplained skin lesion should be checked by your primary and/or dermatologist. A simple biopsy is sometimes all that is needed to make a determination of its cause. Especially for unexplained lesions that change color, these need to be checked out by a doctor.