That's what I learned, that you were just popping something in between you joints or some shit. I have a bad memory and I'm dumb. Besides, even if it did harm your fingers, I would still do it.
Its forming and popping bubbles of dissolved oxygen in the fluid that cushions the cartilage of the joints, I have a similar problem with my knee but that's because I have too much fluid, it sometimes leads me on some spectacular and unexpected trips when one pops at the wrong time.
Nope, doesn't have any affect on the size of your knuckles long-term. A gentleman once popped the knuckles on one hand for many years to show that it made no difference between the two hands. I'll try and find his name.
Correlation not causation. The right hand naturally had bigger knuckles so it had a bigger air pocket =cracks more.
Smaller knuckles = less air = doesn't crack
https://www.scientificamerican.com/article/crack-research/
Smaller knuckles = less air = doesn't crack