Chest pain and arm numbness can easily be indicative of heart disease. These symptoms can actually mean that you are having, or about to have, a heart attack. You should seek medical help immediately. Since you bought up smoking, another ominous condition could be a lung tumor near the very top of your lungs. This can cause chest pain, and can grow outward to invade the brachial plexus which is a nearby large nerve bundle that runs into the arm (causing arm numbness or pain), and can also cause neck pain. Other less serious conditions could include a cervical disc herniation or other musculoskeletal problems. In short, go seek medical help.