For a few years, I've had this hard lump on my scalp. I have tried to squeeze, pop and drain it but the only substance that comes out is blood. I recently tried again to see if there was any pus or clear fluid and there was not. It was a loud pop and nothing but blood came out. Now the lump is bigger. It sits on the edge of my right parietal ridge. Any ideas? I also have systemic lupus mixed with a variety of health issues.