May 30, - What should you do about a pimple on the penis? A pimple may Cysts are pus-filled spots that form underneath the skin. They can appear on. Feb 21, - They usually aren't harmful or a cause for concern. Cysts usually don't appear on the penis, but it is possible. In many cases, penile cysts won't cause any pain or discomfort. Cyst-like bumps may be a symptom of a sexually transmitted disease (STD).Cyst or STD-related bump? · Cyst types and causes · Diagnosis · Treatment.