What Could Be Causing A Dry, Raised Patch From A Pimple That Hasn T Gone Away?

I had a pimple in July. I have had acne my whole life so I am confident in saying it was a normal pimple. I let it be, and instead of coming to a head or going away, it has been a dry raised patch ever since. It never gets dry enough that I can peel the skin though. I keep putting moisturizer on it, no difference. I tried treating it like a pimple and used those Clearasil patches on it. No difference. What could it be or what else can I try?