Renato Sanches's late goal earned Lille a 2-1 home win against Montpellier as they consolidated third place in Ligue 1 on Friday.
They trail second-placed Olympique de Marseille by three points and lead fourth-placed Stade Rennais by four.
Leaders Paris St Germain, who have 39 points from 16 games, travel to St Etienne on Sunday.
Delort, however, equalised in the 74th from close range after being set up by Florent Mollet, only for Portugal midfielder Sanches to give Lille all three points with a fine effort from inside the area.
Lille were still under threat and missed a chance to wrap it up for good two minutes from time when they were awarded another penalty for a Mollet foul on Luiz Araujo.
Osimhen's spot kick, however, was parried by Rulli, but Lille kept their advantage by playing safe until the whistle.