Brown spot on my dog's prepuce

noticed this brown spot on the tip of my 9-year-old Yorkshire’s prepuce. I don’t know if he had it before since the area was always covered with hair. He doesn’t lick himself and there are no discharges. Should I be worried? Thank you in advance.  

Hello and thank you for your question.  What happened to the hair - did it fall out?  In any case, it is worth showing this to a vet who may be concerned about ruling melanoma in or out or (perhaps less likely) localised infection.

Most cancers of the skin or preputial area do not cause pain or produce discharge, so I'm that an absence of these things is insufficient to rule them out and your vet may ask to carry out tests.  Please will you let us know how you get on?