My nephew hit my new LCD TV! Did he damage it?

He's 2 years old and hit my LCD with his hand; the impact was like a hard knock on a door. The section of the screen he hit flashed white on impact, for about a quarter of a second, but nothing really happened. The TV works just fine. But did it cause any internal damage? I don't think he damaged any pixels whatsoever, because I examined it closely and did not see any dead pixels. But did he sort of "taint" the TV? Did he decrease its quality and lifespan? I still have the 30 day warranty from Futureshop; should I make up an excuse and exchange it, even though it works perfectly fine?