I found a lump at the bottom of my back that is small, pink and brown around the edges?

I found a lump at the bottom of my back that is small, pink and brown around the edges. What could it be? I am quite concerned as I have only just noticed this and it is not painful. I think it has been there for a few months now, I have nothing else on my body and I have had blood tests and they are fine

Age: 21
Male
Medications: None

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