Yes, it's a one-game win, and Chelsea played exceptionally well in that match. Perhaps they'll face Paris Saint-Germain again in the Champions League and not play the same way. Perhaps they'll play the same way and beat Paris Saint-Germain again—time will tell. Chelsea drew their first Premier League match, but because every match is important in the Champions League, they should strive for more wins.
They may not even meet in the Champions League as a whole. Their first match in the EPL was strange because they dominated, shot at the goal, but were unable to break through the defense despite their colossal dominance. In the Champions League, this would be a critical mistake, and they cannot afford to make it. I think they understand this.