What Causes Penis Frenulum Fissure?

i have penis frenulum fissure-just a small tiny round cut. i seen a dermatologist a month ago.He presecribed cicalfate cream. i have not had sex neither masturbate for 1 week after the visit. but i masturbated on the second week after the visit, it reappeared again.However, it does not bleed, but it's painful.