Hello and thanks for posting on this thread.
I am sorry to learn you have an ache that you are concerned about.
Many people contact us because they are concerned that symptoms they have might be caused by cancer. We are unable to diagnose you and the best advice we can give is to go and see your doctor. They are very used to being asked about all sorts of things, and will put your mind at ease.
Although this can sometimes seem frightening, in most cases your dull ache in the testicle will be caused by something else other than cancer such as an infection, or muscle strain. But it is always sensible to get any problems you have checked out to be on the safe side.
There is information about testicle problems here,
And also information about how testicles should look and feel,
I hope that this has been helpful.