Hello I had gone through your question very diligently and I can understand your concern A small lump followed by pus discharge might be related to Inflammation or infection of the penis. Here I would like further information for better assessment of the condition Since how long you have this problem any history of unprotected intercourse? If I were your treating doctor I would have advised you for battery of test like blood for hemoglobin, CBC, Liver and kidney function test, blood sugar, urine testing for microscopy as well as culture. In my opinion you should clean it thoroughly with antiseptic solution and apply mupirocin or clotrimazole with betamethsone ointment for 3 to 5 days. Meanwhile you should take plenty of fluids 3 to 4 liters a day. You can take Ibuprofen for pain . Avoid sex or use condoms until you recover fully Please feel free to ask for more clarification, I will be happy to help you Best wishes