The striker scored the Yellow Canaries' second goal after Kalifa Coulibaly's opener but the away side mounted a strong fightback to ultimately claim a 4-2 win at Stade de la Beaujoire.
Nimes pulled a goal back through Baptiste Guillaume two minutes after the interval, while Antonin Bobichon levelled the score by the 69th minute, with Jordan Ferri and Sada Thioub sealing Les Crocodiles 4-2 triumph.
Nantes currently sit 16th on the league table while Nimes occupy the 11th position.
Waris, who is on a season-long loan from Portuguese club Porto, now boasts of four goals in 22 league matches involving 14 starts so far this season.
The Canaries will play away to Caen on Wednesday.