[ Singles & Dating ] Open Question : Was this ok for me to do?

I'm a 16 year old girl called Jade, and recently, my ex boyfriend who i dumped has been really upset, and he's been bugging by best friend cuz he's mad at me and wants her to suffer. He's been a real jerk to her and when i saw him bothering her again after school, i confronted him and said "Can i talk to u for a sec?" He said sure thinking i was gonna take him back, so i pulled him aside and gave him a little knee to his nuts. He immediately fell down to the ground writhing in pain, cupping his balls and sweating, moaning, etc. I didn't know it'd hurt him that bad. I just wanted him to bug off a little. I didn't know he'd be that hurt. I mean, how much can a little knee to his balls hurt? I was trying to help my friend.