I happened upon this post and thought I would throw my two cents in. In all honesty, I would not worry about it, unless pain becomes a part of it. I would think that many will experience this sometime during their life. You can almost ask anyone...and they will tell you that they too!... have had some sort of poping and cracking noises somewhere withing their body.
Now of course!...if pain is associated with it, then by all means, make an appointment to have it looked at. Just be careful testing for pain...because we all can induce pain once we hit the limit of turning our heads too far.