<s>[INST] Last night I noticed an irregular-shaped  brown spot on the head of my penis. It does not appear to be raised and is painless. I am sixteen and not sexually active although I frequently simulate sex while clothed with my partner. I also regularly masturbate and it was while doing so that I noticed the spot. I am worried as to what this is and if it will go away. [/INST] Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice.You might be suffering from Zoon's balanitis or Plasma cell balanitis which occurs due to irritation of foreskin over glans penis. Apply Fusidic acid cream for 2 weeks. If you do not get any improvement or if you are having other symptoms such as urethral discharge or genital ulcer, immediately consult your Dermatologist/Venereologist.Hope I have answered your query. Let me know if I can assist you further. </s>