Hello Thanks for query .Based on the facts that you have described the painless lump since last 2 years that your boyfriend has is a Sebaceous Cyst over scrotum . The scrotal skin is rich in sebaceous glands and hence prone to get more sebaceous cyst due to accumulation of sebum beneath the skin. Normally it fades away without treatment however they need to be treated if increase in size or get infected. Please consult qualified General Surgeon for clinical evaluation and further treatment. Since it is there since 2 years and of a size of peanut it needs to get excised in Toto under local anesthesia . This is a simple surgery done under local anesthesia as a out patient procedure and offers permanent cure . Dr.Patil