City hold a slight advantage at the halfway stage of the tie having scored two away goals in Paris ahead of Tuesday's second leg at the Etihad Stadium.
Pellegrini acknowledged that it is a good result for his side, but admits that they need to cut out the sort of mistakes that led to PSG's first goal.
"The quarter-final continues to be open, we must now play 90 minutes in Manchester but this is a good result for us," Pellegrini is quoted as saying by BBC Sport.
"We made a couple of important mistakes for the first goal and the second goal was offside. In the first half, if we want to win, we cannot make those kind of mistakes.
"But we are trying to win the game from the first minute, it is the way we play."
Man City are appearing in the quarter-finals of the Champions League for the first time in the club's history.