What is a gram positive bacteria that would cause hard, painful cyst down there?

An Infection. Gram positive bacteria are usually staph or strep infections. As the cystic pocket fills with the pus or bacteria it will start to become hard or firm over time. At this point antibiotics may not be helpful and therefore drainage or removal of the cyst is usually required. Don't let this drag on, as this will then start to damage some of the good tissues that are close to this area.