Blanc's men won 1-0 away at mid-table Nice to open up a 13-point buffer at the helm of Ligue 1 as they canter towards consecutive league titles.
However, Blanc was concerned with his side's forward prowess - as their winner came via an own goal to Nice defender Timothee Kolodziejczak - ahead of their first leg against Chelsea in the UEFA Champions League quarter-finals.
"This is a very important victory for the championship. There were a lot of good things in this match, but we also wasted a lot of chances," Blanc told the club's official website.
"The problem is we don't move fast enough in attack.
"We have to be a lot more ruthless in the opposition penalty box.
"We need to fix that ahead of Wednesday's Champions League match against Chelsea."
Blanc said their overall performance against 11th-placed Nice was below par, but the winning feeling was important for PSG ahead of their blockbuster with Chelsea.
"We came here looking for the result, and while we didn't play well, we got the job done," he said.
"The matches before a Champions League game are always difficult so it's a good thing that we got the three points tonight.
"I said the best way to prepare for Chelsea was to win tonight. It wasn't our best game, but you have to know how to win games like this."
PSG front man Edinson Cavani said he was thinking ahead to their European encounter during their visit to Nice's Allianz Riviera.
"The important thing was to win," the Uruguayan said.
"We have three more points so we fulfilled our objective.
"Obviously we all had the Chelsea match in the back of our minds, but now we can really concentrate on this game and recover well so that we're ready."
