Pain is a symptom of being hurt or sick. It is a bad sensation that is physical and emotional.
Most pain starts when part of the body is hurt. Nerves in that part send messages through senses to the brain. Those messages tell the brain that the body is being damaged. Pain is not just the message the nerve sends to the brain. It is the bad emotion felt because of that damage.
The message that the nerve sends to the brain is called nociception. What is experienced because of the nociception is pain.