It's not a secret Satoshi Nakamoto has more than 1 million of Bitcoins in his wallet, right?
If he suddenly wants to sell all his Bitcoins, could it cause a chaos in Bitcoin market making the price fall? Or is this amount too insignificant to cause any mess?
Yes .Bitcoin market will be fallen.1 million bitcoin is huge amount of bitcoin. If he sell all of his coin in one time, the effect will be decrease the rate of bitcoin.
Even if he did not sell all his coins, if at some point it is discovered satoshi, the creator of bitcoin is selling his stash, then everyone will begin to panic, if even the creator of bitcoin is cashing out, why I should stay?, as you can see it is not only the amount of coins we need to be worried about, just the act of satoshi cashing out come coins will be terrible for the network since people may lose faith in bitcoin almost overnight.