I've injured two knuckles trying to get them to crack when they wouldn't. Eventually I broke the habit of cracking knuckles at all to prevent further injury.
For those who read about the doctor who popped one hand with no issue is only a sample size of one and he only popped the knuckles on that hand once a day. When I started trying to break the habit I was tracking and I'd often crack a single knuckle 30+ times a day and did for 20+ years.
Crack responsibly, unlike me, and you're probably fine.