So, I'm guessing it's just the after affect from sex like a friction burn or little abrasion and when urine hits it, it burns. And then hurts from time to time. This happens. Maybe you were not quite lubricated enough during sex? As long as it doesn't burn inside while your urine stream is ending (which would mean it's more like a UTI)-- then this is probably something that is healing after sex. And it may start itching next as we often do when healing. You can try a spray bottle of warm water and you squirt it on there as you pee. They have women do this after child birth (the holy mother of abrasions, tearing, etc. of that area). You can try a tucks wipe that you just leave in your panties (another after birth trick). Prep H ointment is also used believe it or not. All will sooth and aid in healing. Hope it's better soon. good luck