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As you are not able to retract fore skin of of your completely and a pin hole only appears after possible retraction, your son seems to be suffering with Phimosis
. He might have developed infecyion also due to collection of smegma
is best possible treatment. It is a simple surgery. you should consult a general Surgeon
for examination and treatment.
Hope you found my response to your query informative and helpful.
With good wishes,
Dr.Chandra Shekhar Sharma