I got them a lot and it did hurt for hours
Long ago when I was 16 I had a girl friend for a couple of months in the summer. She had come with her mother to visit her grandparents and we met a couple of weeks after she came to our town.
The first time we went out we immediately got quite serious and I ended up parking in a favorite spot with my hands all over her. She let me take off her panties and I felt all over her bush and vagina. Oh how I loved that smell and sweet slippery feeling. After taking her home I headed quickly home and jerked off to the new smells.
As time progressed we got a little more daring, but in those days I didn't know enough to be able to get her off, so we just enjoyed the intimacy. One overcast day we went swimming and there was no one else there. In the water she suggested we just slip off our suits and skinny dip. This lasted for 15 minutes when I was so hard it hurt. And then it started to lighten and rain, so we slipped our suits back on and headed to the bushes to change. I immediately started to jerk off but couldn't come before I heard her call to me to hurry up. That just ended the moment and I dressed.
When I got to the car she asked why I was so slow and I just mumbled that I was trying to keep my feet dry before putting on my socks. She just kind of smiled and said, does that tent in your pants have anything to do with it? I was shocked to have a girl catch me out like that, but blurted out something like, yeah, it hurts. So, she wanted a full explanation of blue balls. I said that whenever we were intimate, kind of like skinny dipping, I would get excited and ready for more, which never happens. The result is that all the sperm has nowhere to go and it backs up into the system causing very sore testicles that lasts for hours.
Her next question nearly knocked me over when she asked is there a way to relieve it. I answered that there was a way but she might not be interested. Her response, I guess normal for a 17 yo, was that she would love to know how to relieve it.
With this we drove to a more secluded spot and she had her first encounter with my penis and watched as I started to jerk off. She wanted to touch it and said how nice it looked as she did some of the jerking. She tired and I finished it off into a napkin from the glove compartment. Immediately I felt really accomplished and yet a fool because the feel goes away immediately and there I was with my cock in my hand and my pants on the floor of the car. She thoroughly enjoyed the episode and we did it a couple of more times.
Oddly, she never asked for me to help her and I always thought that although she enjoyed the feeling of sexual excitement she hadn't yet figured out how to finger herself to an orgasm. It was not as common back then as it is now and there was no sex ed to guide and educate the kids. We broke up over the winter after she went home, but that experience lead me into several more 'blue balls' recoveries in the future. Fun stuff.