5 Days Back I Had Sex To My Wife While

5 days back I had sex to my wife while she was on her period, we were out for the weekend so I didn't have a chance to shower right away. I had alot of her discharge on my penis for more than 18 hours. 2 days later it felt like a had a cut or something under the head of my penis, the next day I had a dark area on the right side under the head. I had what looked like burnt skin hanging loose, I lost the top layer until it was raw which was very painful. The area seems to have grown, it seems to be dead skin, I'm hoping it will just heal but I am a little worried. For the record I have been with the same woman for 6 years and never had anyone else. Please advise