I Found What I Thought Was A Pimple On My

I found what I thought was a pimple on my upper right are last year. I tried acne creams & scrubs but it persisted. I started squeezing out the white pus nightly. I went to a dermatologist. He made an insision. That is healing but a large hard spot under the skin was growing. Before I went to bed Sunday afternoon. I noticed there was a huge white head of pus in the incision spot on my right bicep. The site was hard, achy/itchy and red. I impulsively squeezed it slightly. It oozed the most pus since I noticed the spot. I had a sensation of relief (and discussed, it's really gross). I can no longer get it emptied. There is a persistent hard lump the size of a raisin under the skin. I did give it several more hard squeezes this morning and nothing comes out.

I want a second opinion on treatment.