Thank you for your query.
This might be an infection in the urethra
, or an injury/abrasion to the urethra. You need to have his urine checked for infection. If that is not the problem he must see a urologist
for a examination. Discuss with him in private to make sure there's no risk of any sexual abuse. Make sure that his personal hygiene is adequate, And that no habits of his could be causing this. I trust this information is helpful. Please feel free to ask for any other queries.