Hi, If it’s not sexually transmitted disease then it can be – Acne , Fordyce spots - which develop when skin s pores are clogged with natural oil, called sebum, sweat, dead skin, it can also cause infection Pearly penile papules - small, fleshy bumps that usually develop in gland penis in rows around the head of the penis. Skin tag – its normal , happens in age advances Lichen planus - Ingrown hair which is painful can leads to infection , needs medical management Rough Masturbation/Sex Pemphigus If its sexually transmitted Disease (STD). It can be 1.Herpes - Genital warts (HPV) can be diagnosed by the presence of very painful blisters , sallow ulcers or red base. There are treatment options for genital herpes, but there is no cure. As to the treatment, it is based on relieving basic symptoms, early healing as well as the decrease of symptoms duration 2.if it’s not painful- Syphilis, diagnosed by Blisters appear as the first symptoms of primary syphilis. They usually disappear on their own with time, but remains in the body. first blisters on penis appear, important to seek medical help. 3. molluscum contagiosum - small, painless bumps. 4.Yeast Infection- It causes blisters, redness, itching and swelling. Blisters are usually white-colour and thick. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. S.R.Raveendran, Sexologist