Pain ?

[vic1225]

I was doing some observations on my 3 year old nephew when I was babysitting him. We were playing outside and he fell off a rock, scratched his inner forearm badly. He immediately looks at me and has the crying look on his face, but I turn the other way and he continues to play. When he is around his parents he will bump into couch and start crying. My question here is pain a natural instinct or is it learned, do we change the amount of pain we can endure to who ever is around us.