Welcome to HCM.
It might be due to some infection in the urinary tract
It also occurs during passage of small stone and crystals .
it is commonly seen in passage of semen in tract after sex or masturbation
Go for urine,cbc,fbs,ppbs and usg abdomen to rule out proper diagnosis.
Drink more water and other liquids.
Get examined by dermatologist
to rule out any local condition.
Keep proper hygiene.
Consult your physician for guidance and proper medical management.