What Causes Swelling And Purple Color Underneath Of Ingrown Hair Follicle?

I think I had an ingrown hair before...so I picked and picked until it finally scarred but I was never able to retreive any hair out of it...I finally left it alone because I was scarring from it...it hasn't bothered me except for the fact it is ugly...no all of a sudden like months and months later it just swelled up like the size of a marble and has a purple color underneath...what could it be?