Hi ! Most likely you have multiple sebaceous cysts of the scrotal skin, which are getting infected after you scratch them. Do not try to scratch them. They are formed due to blockage of the sebaceous glands from where the secretion called sebum can not get drained and gets accumulated. They are benign problems except for discomfort as you have and they are not due to STD
. However, if you are sexually active, then you should go for some investigations after consulting your family physician who may also advise you to consult a surgeon for their removal. Wishing you an early recovery.