My little bro has back pain?

My little brother skates and he was at a skatepark. He tried a 4 1/2 foot ledge and landed it once. He tried it again, and again, and again, but couldent land it. each time he kicked the board out, he landed on his feet and bent his back a lot each time. His back has been hurting him for about a week and i need to know how to fix his back. (it hurts right below the middle of the back)