Question
I have had a very sore neck for a couple weeks that has also been causing a headache. There is a certain neck exercise recommended for neck pain, where you retract the head and neck back with your chin pressing into the chest. When I do this, I notice a nerve like pain in my upper arm and it's only my right arm for some reason. Can you tell me why this occurs and is it harmful to continue? Thanks

Answer
i would not continue with any exercises right now. Your headaches are most likely tension headaches AND EXERCISE WILL INCREASE TENSION IN YOUR NECK, therefore increasing headaches. The upper arm pain you are having is because of a pinched nerve in your neck (cervical spine). some of those nerves in lower cervical spine run down your arm controlling sensation and the muscles of the arm.
go see a chiropractor and give yourself 4-8 weeks to heal from this. if you have a history of headaches , then you may want to see him a few times a year for check ups (like you do with your dentist).  good luck!