Should I be worried about a red mole that turned black

[Herrera1]

I have had a mole that has been on my upper back for about two years. It has always gone from red to white to purple or black month to month. It is about the diameter of a pencil eraser and is mostly circular. Recently I scrapped it on the bottom of a pool and it bleed quite a bit. Two weeks later it still hurts to lay on, is black, and is now bumpy. (It is a muffin shape now) A red and purple rim around it has been forming and now white skin like flakes and bumps are around the edge and on top. Not sure if this is all because of the scrape or not, it seems like it would have healed by now.