That is an excellent question and one that is best answered by your primary care doctor
or a medical specialist in the field of neck pain. He or she will be able to evaluate you based upon your history and physical examination and decide upon the cause of this knot and pain you are experiencing where your hairline begins. Because of the limited history provided, it is difficult to tell you the exact cause of your symptoms but here are some potential causes for this pain that you are having and some symptomatic treatment options available until you can be seen by your doctor and he or she can decide upon the appropriate treatment options available for your specific symptoms. One of the most common reasons for this is that you have a muscle sprain, possibly caused by lifting a heavy object or sleeping in a bad position. You can try ice or heating packs and advil to try and help with these symptoms. On the other hand, there are much more serious causes for this that are outside the scope of this discussion, and for this reason it is important that you are evaluated by your doctor to find out the cause.