Blanc's men extended their lead at the top of Ligue 1 to 13 points ahead of Monaco, who visit Evian on Saturday, with the victory at the Allianz Riviera.
However, PSG were made to work hard for the points, which were secured seven minutes into the second half through a Timothee Kolodziejczak own goal.
The result marks the second time in as many weeks that the defending champions have claimed an unconvincing 1-0 success after doing the same at Lorient last Friday.
And Blanc will demand better from his players when they host Chelsea in the UEFA Champions League quarter-finals first leg at the Parc des Princes on Wednesday.
"This match will not live in the annals of PSG," Blanc told beIN Sports. "But the job was done.
"We came here to take three points for the second consecutive trip after Lorient.
"The problem is that for the last two or three matches we have not been forceful enough offensively.
"In Lorient we had the first 10 minutes where we had more opportunities and should have been more effective.
"We will be effective on Wednesday against Chelsea. We will be very, very effective."
