Valentin Eysseric's first goal of the season dealt a blow to Lyon's title hopes as 10-man Nice snatched a late 2-1 win.
PSG went top of Ligue 1 for the first time this season after title-rivals Lyon lost 2-1 at home to 10-man Nice on Saturday.
Lyon moved two points clear at the top of Ligue 1 after drawing 0-0 with Marseille, while PSG lost 3-2 to Bordeaux.
Marseille and Lyon cancelled each other out in a tense goalless draw at the Stade Velodrome.
Lyon striker Alexandre Lacazette admits his future is up in the air and he could leave the Ligue 1 club in the summer.
Lyon moved top of the Ligue 1 table following a 5-1 comeback victory over Montpellier.
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