Welcome to HCM,
At this age there might be having some infection,fungal or bacterial due to poor local hygiene.
Clean local part properly with warm water while taking bath.
Apply antibiotic, anti-fungal cream locally.
Wear short having elastic at both thigh leg part so that any dust enter on local part.
Use cotton nicker or short.
For itching give some antihistamine like Cetrizine
Give plenty of water.
Ok and bye.