Joe gets traumatically castrated, either in a horrible accident or someone does it to him as a deliberate attack/torture technique (by this I mean not consensually for pleasure). I'd be interested in reading any/all of the following, or your own twists on:
1. Joe's fear of it not growing back/healing properly
2. it growing back painfully slowly
3. Nicky taking care of him while it does or doesn't grow back
4. Nicky's feelings about the situation
5. first time they have sex after it's healed (in however way you decide it does)