What are the small white stones on my scrotum?

Every hair follicle has a gland that secretes sebum to lubricate the hair. If the hair falls out the gland keeps going. When sebum hits air it turns black. That is why you have black spots all over your nose and cheeks. If the pore is closed by skin then the sebum remains white and you have a whitehead. Whiteheads are very common in the crotch. They probably won't cause any trouble. Big dark spots are ingrown hairs. Scratch lightly and they will pop out.