I had this the other week, sounds like AIDS to me - I just walked it off...

but in seriousness it's just from too much sex. Like Phil said STI's take a few days to manifest!

If anything get canneston like knave said or a feminine cream to put on there, it will moisturize the sore area and encourage repair. I haven't found any creams made for men but feminine creams are really subtle and effective.

Get checked for STIs too but you'll be fine