Feel free to crack your knuckles all you want...who cares if it sounds hideous and drives your coworkers insane? It's not screwing up your body.
There's an old wives' tale that cracking your knuckles can cause Arthritis when you get older, but studies have proven that's just a myth. You're just popping air bubbles when you crack your knuckles, not messing with your joints. Seriously.
Technicall, when you crack a knuckle, you're forming and then popping an air bubble in something called your synovial fluid; the stuff that reduces friction in your joints.