What is under my skin?

I picked a sore on my arm for several years. I let it heal two or three times but then started picking it again. Three months ago I let it heal.completely. It the scar is bluish in color and about two inches around from side to side. Now it is itching so bad I can't stand it! It feels like I have stinging nettles under my skin and the itching is unbearable. Could there be some bacteria or fungus or something else under my skin. Today I got angry because it won't go away and I dug across the scar with my fingernails putting scratches. My mom put oregano oil and a healing lotion on it but I want it to go away. I don't want to have to pick it anymore. Please give me feedback. Thank you