This could be a ssebaceous cyst of the scrotum.A sebaceous cyst is a closed sac or cyst below the surface of the skin and fills with a fatty white, semi-solid material called sebum. Sebum is produced by sebaceous glands of the epidermis.
In males a common place for them to develop is the scrotum and chest .They are more common in hairier areas, where in cases of long duration they could result in hair loss on the skin surface immediately above the cyst. They are smooth to the touch, vary in size, and are generally round in shape.
Blocked sebaceous glands, swollen hair follicles, excessive testosterone production, will cause such cysts.
Sebaceous cysts generally do not require medical treatment. Surgical excision of a sebaceous cyst is a simple procedure to completely remove the sac and its contents.