You may have some problems with your neck, such as strained muscles. The cracking noise could be coming from your joints. If you sit with your head bent down for a long time or do not move around much this can happen. It’s important to gently stretch and move your neck. You may want to do some exercises that will make the muscles in your neck stronger too. If the pain doesn’t stop, it would be best for you to see an orthopedist who can give more advice on what's going wrong.