“Blue Balls” is slang for what happens when vasocongestion becomes painful. What the hell is vasocongestion? When you’re aroused, blood flow and blood pressure are increased to the penis, testicles, clitoris, uterus, and vulva, causing them to swell and/or become erect.
This process can become painful, sometimes from lack of climax. It’s more commonly called “blue balls,” because in people with testicles the pain is often felt there but if you have a vulva then your clit or uterus may be what feels uncomfortable. Vasocongestion can also happen during menstruation.
But hey, just because it’s a real thing doesn’t mean it’s anyone’s responsibility to take care of it for you.
Want to know more? Check out Vasocongestion on Wikipedia.