It is very hard to get a photo but here is my best effort.
The black area is all the scabby bit but there is more all over his scrotum.
I cant think it is an injury as it is all over and looks more like an irritation than an injury. It is deep into the fur and the skin underneath the scabs seems pink but clean. It is nowhere else on his body.
I have not noticed him nadging at that area since I have been home and my OH says he noticed nothing strange either.
Vets is absolute last resort as getting him to show the vet that area requires wrestling and big stress and maybe even a sedative he is so freaked out since his op.
Typical, I go away for a few days and this is what happens.............