After three weeks of 24/7 lockup during Locktober, my balls are incredibly swollen and hurting. Any tips?
It's mostly psychological. They aren't swollen, you just think that. Try to think about something other than your testicles.
So long as circulation is fine (no blue balls!) you'll be fine, too. If all's well, the aching should reduce soon enough.
I was getting some ball ache during Locktober which I assumed was due to the weight of the steel cage being supported by my balls. That was toward the end of 21 days of being continuously locked (I'm used at most 7 days of continuously locked in a ball trap device). I was really tired so my Mistress unlocked me for sleeping, after which we switched to a very light 3d printed cage and the ball ache is gone.
Just your body getting used to having the newly placed restrictions you have imposed upon it, it will pass.
You will come to embrace the ball ache. If it gets too intense I beg my Kh for a funishment session. The red welts from the cane and the raised bruises and blisters from the studded paddle take my mind right off my balls for some reason.