I have a spot on the back of my leg, it's not painful and hasn't bothered me just scared it could be something serious? (photo)

Location: Back of Thigh, Color: Red in the middle with Brown discoloration in a small patch of surrounding skin, Size: About half the size of a Pencil Eraser, and I'm not sure exactly how long it's been there but I first noticed it almost a year ago, also it seems to change periodically it'll grow out almost like a pimple then other times such as now it's flat so it looks just like a patch of discolored skin at the moment.

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