Fixed drug eruption. Skin takes place?.

I had a fixed drug eruption by secnidazole medicine dosage. I was completely fine before that, my wife's was suffering from bacterial infection, her gyno suggested to complete FAS kit and she went fine after taking this kit. Gyno suggested me also to take this kit to completely avoid this infection transfer in future. The day I took 500 gm two secnidazole tablet, after 25 mins I started having it in in my penis head inner skin, it became red and next day turned black and started peeling off. I went to dermatologist and he said it's common and just FDE. I am taking medicine now and appying ointment too two to three times. But skin on half of penis inner head has turned red and can't place even my finger on it properly.  itching has gone. I just want to know how does healing of penis inner skin takes place?. It's been 5th day of treatment but minor areas have got cured. Total it's 10 day treatment which I am receiving.