When you first experience pain, it is a symptom of illness or injury in the part of your body that is having the pain. The sudden onset of pain is called acute pain.  It gets your attention and prompts you to take action to prevent further worsening of the condition causing the pain.  This could be a simple action such as the reflex that makes you jerk your hand off a hot stove, or it could be more complex such as cooling, resting, or elevating an injured ankle.  Or the pain could prompt you ...