it's true that keeping oneself busy is the most important factor to be successful in NOFAP, but, does this mean that doing activities or exercising and getting busy will relieve the pain and most importantly the harms of getting blue balls?
Redirecting the blood is a good way to relieve the pain of blue balls. It would also be helpful in the long run though to start taking a supplement or eating herbs that reduce inflammation, and/or take cold showers.
So there is a book called The multi orgasmic man, in the book you want to learn how to orgasm without ejaculation, in the beggining it is said to massage your testicles and focus on deep breathing when you get congestion ( blue balls) . I have been doing it lately and in 5 min the pain is gone and also the sexual tension in that area. Take a look at the book if you want, I recommend it. It is available online. Hope it helps!