I think the fact that Nice is strong and playing well against PSG this season will be additional factors to motivate PSG players and to play the best of their abilities. The bookmakers estimate PSG's chances of winning at 1.85, which I think is a very favorable odds. An additional factor in favor of PSG is a longer rest than Nice - they continued to play in the French Cup.
PSG are focusing on the UCL match next midweek and on the domestic league they won't have any effect when they fail to get points, I think in this match PSG will play with their back-up players while the main players will be saved against Real Madrid, and so it's huge Nice possibility can take advantage of that and win this match.