Heart attacks can mimic neck pains that pinch nerves going into the left arm. Additional symptoms that accompany the pain are added clues. Some of the most important are related to all the nerves that pass through your spine on their way between the brain and the rest of your body. These nerves send feelings in one direction and movement commands in the other. Certain changes in feeling like tingling, burning or extreme sensitivity are also signs of nerve problems.
Paralysis is the extreme form of weakness.
The urinary bladder can also be affected by nerve damage related to back pain. So if your back pain comes with inability to control urinating, there is likely to be a significant relationship between the two. If pain isn't present, it doesn't exist. If your pain is clearly related to what you are doing and has no peculiarities like numbness or weakness associated with it, chances are it's just mechanical strain. But any pain that lasts more than a few days without improving, that has no obvious cause, that gets worse without provocation, or that has associated symptoms, should get you to a physician without delay.