Rest, stomach breathing. Your muscles might be tense/swollen around your inguinal canal, which might pinch off the nerve a little (or you did while working out), causing that kicked in the balls feeling.
I had hernia surgery a few years ago, and often (well, more often than I would like to) get this feeling. Sometimes it lasts days. One time it lasted a few weeks... Not sure it applies the same but it's at least somewhat possible.
Hope it's not hernia.