The most common cause of a penile "bump" would be Herpes (HSV). Herpes comes in two forms: HSV-1 (usually affects the mouth) and HSV-2 (usually affects the genitals). The herpes virus can be transmitted even if you are using condoms and even if you don't have any symptoms. Most doctors do not routinely screen for Herpes because most people have already been exposed. Unfortunately, once you have HSV it can never be cured. There is medicine that your doctor can presribe to shorten the duration or severity of an outbreak.