Have a small pea-sized lump on my back between l. shoulder blade & spine. hard. no discharge or pain. no color.has remained same size for about 2 yrs.

Cyst or not: Most commonly this would be a "lipoma", which is a lump of abnormal fat, or a sebaceous cyst, which is kind of chronic inflammation from old trauma. An abscess could also be a cause. If not enlarging and not painful, red or draining, safe to watch. Treatment is surgery to remove it, which is low risk, minor, and outpatient procedure.