I was going to ask the same thing to be sure and this is what I found:
yellow cards from first group stage do not get carried through to the knock out stages. however if you pick up 2nd booking in last match you're suspended
However, I am interested to know if a yellow card in the second round for example, and another in the quarter finals (two successive matches that is) would bar you from playing in the semi-final? I know if you get a red in a certain game, then you are off from the next one, and this applies to both the first round and the elimination round.
ASHOOR