Many years ago i went the docs with acheing nuts , apparantly nut and back pain is somehow connected (its the back that transfers the pain and you feel it in your man bits) .
Mine went eventually but it wasn,t nice ! It could and probably is just a bad back like millions have and you are just unlucky like i was and your nuts ache .
Glad you have had the all clear mate so try not to worry .

Its not just me then who can,t type testicle .