Normally, with a hernia, part of the abdominal contents protrude through the tear in the muscle wall. The greater the pressure in the abdomen, the more the contents protude. There is usually some minor discomfort with this. Usually the protruding contents slide back into place on their own or are easily pushed back into place with light pressure.
What becomes a concern is when the contents are not readily pushed back through (reduced) the muscle wall opening. This is refered to as an "incarcerated" hernia, which becomes a medial emergency requiring urgent sugical intervention. You will experience a pretty good amount of pain should this occur.
You won't necesarily notice problems with testicular movement at any time, related to this condition. It really doesn't directly involve the testicles, other than the potential for the hernia sac to press on some of the associated vessels and ligaments.
At some point in time, surgical repair will be necessary. As I said earlier, inguinal hernias never get smaller.