Hello I share your concern, I had gone through your question diligently and I will try to help you out in best possible way Pus filled pimples on the testis can be caused by infection from urine or stool and sexually transmitted infection or multiple sebaceous cyst and can be allergic as well If you can upload me a photograph and answer my these questions I will be able to help you better Your age and relevant medical history if any like diabetes or liver disease? Have you ever had similar problem in past In my opinion you should see your doctor for physical check up and investigation to rule out infective condition Meanwhile you can apply antibacterial or antiseptic ointment like mupirocin Maintain good hygiene you can take Ibuprofen for pain. Hope this answers your question, Please feel free to ask for more clarification, I will be happy to help you Best wishes Thanks and regards