Nice won 1-0 on Sunday to extend Lille's winless streak in Ligue 1 to five games.
• Ligue 1: Saturday review
Nice defender Mathieu Bodmer diverted in Christian Bruls' volley with a back-heel flick on the stroke of halftime to secure the victory for the hosts.
Despite the defeat, Lille remain in third place but saw their lead over Saint-Etienne cut to one point after picking up just two draws and three losses from their past five league games. Nice moved into 12th place.
Also on Sunday, Marseille lost the lead twice to draw 2-2 with Toulouse.
Marseille winger Dimitri Payet opened the scoring with a diagonal strike in the seventh minute before Toulouse forward Wissam Ben Yedder leveled from a corner redirected by Martin Braithwaite in the 11th minute.
The hosts recaptured the lead in the 40th minute when Andre-Pierre Gignac cut the ball back for Marseille playmaker Mathieu Valbuena, who slammed the ball into the net.
But Toulouse defender Serge Aurier beat hesitant goalkeeper Steve Mandanda to the ball to head in a corner in the 60th minute.
Marseille stayed in fifth place and Toulouse slipped to 13th.
Lyon suffered a setback in the race for a European spot as they lost 2-0 at Rennes, who sit in 15th place.
Defender Cedric Hountondji put the hosts ahead by heading in a corner from Romain Alessandrini in the 22nd minute, and Lyon then went down to 10 men in the 41st when defender Samuel Umtiti was red-carded for a violent tackle on Alessandrini.
Rennes striker Ola Toivonen doubled the lead in the 66th minute by taking a pass from Abdoulaye Doucoure to fire home a low strike.
Lyon trails fourth-place Saint-Etienne by six points.