It's not bad or harmful to pop your knuckles but it doesn't really do much of anything either way.
The cracking of your knuckles or popping of your knuckles helps provide temporary pain relief when your hands or knuckles are feeling stiff.
But it only provides temporary relief.
Also contrary to popular belief popping or cracking your knuckles does not cause arthritis.
When you pop your knuckles you basically release some gas build up which provides the relief.
But the gas returns soon after and you'll need to pop your knuckles again.