Cracking your neck is okay when done correctly and when done in moderation.
If you're cracking your neck too often or not cracking your neck correctly then it can be bad and lead to pinched nerves and cause the ligaments in your joints to get permanently stretched which is not a good thing at all.
Cracking your neck can help you feel better when you have a stiff neck but if you crack your neck incorrectly or do it too often then you can have more than just a stiff neck.
So I would only crack my neck when I absolutely needed too and if you're unsure of how to crack your neck properly you should have a trained professional do it for you.
Or study up on how to actually crack your neck correctly because you do not want to cause damage to your neck or body from incorrect cracking of your neck.