Hi there ~
I believe that you have a reason for being concerned about your testicle becoming non functional after the removal of the cyst
which is currently benign and not showing any signs of enlargement. Most epididymal cysts usually are so, and reduce in size and ultimately disappear over time. It happens due to infection or inflammation and there is no treatment except to treat the infection if that is the cause of the inflammation. I hope this helps.
Take care and have a lovely day!