You are supposed to be able to turn your neck to the left and right, equal to shoulder. If you can't do that, you are experiencing limited range. That can be fixed very easily. The same thing goes for tilting your head up and down. If you can't put your head allllll the way back, and then bring it back forward and rest your chin on your chest, you have limited range. Once again, a chiropractor can fix that very easily, with spinal decompression, or traditional chiropractic manipulation.
There are only seven bones in the neck, but they can easily get out of whack. A simple exam by your chiropractor can find out what is out, and what you need to do to fix it. There are many ways to adjust your neck, a chiropractor is the only person who should attempt to crack someone's neck. Never crack your own neck; a saw a young man in a critical care unit who did that and gave himself a stroke at the age of 23/
Leaving it alone is not the right answer either, that can lead to a number of issues. If you are having neck problems, see a chiropractor right away.