Brief Answer: Single lesion is common Detailed Answer: Hi Penis head has a lot of crypts and if one crypt has some debris and get swollen it resembles pimple. One such pimple has no clinical importance. If it is painful it is infected then needs treatment. Otherwise we would not treat it. But if you are sexually active with more partners and unprotected sex it will be considered a high risk behaviour and treated by doctors. There is something called Pearly papules of penis which look as you had described. Check the photos on the internet about it. You may have an idea. Let me know your thoughts and inputs.