I was performing a self check-up following a painful incident when I noticed a dark, nodular bump on

I was performing a self check-up following a painful incident when I noticed a dark, nodular bump on my skin. It appeared irregular in shape and was oddly multicoloured and variegated. I estimated its diameter to be approximately eight millimetres. Upon further inspection, I found several more in various locations on my body. I corresponded with a younger friend and they seemed to have none, but my older friend had many more. Should I keep track of the evolution of this potential malignancy?