Technically, it isn't a must win.
Scenario 1:
If we draw this and PSG wins against Ajax, we go to 10 and they go to 13. Last game is against PSG at the camp. If we beat them, then head to head is equal and it will go to goal difference.
Scenario 2:
We beat Apoel, PSG beats Ajax. We are still a point behind them. At which point, even if we draw against them, they top.
So really, assuming PSG beats Ajax, we pretty much have to beat them in the last game. A win would still be good and avoid goal difference complications though (We will probably be ahead on goal difference anyway if we beat PSG in the last game, as we are currently 1 to the good compared to them)
Well said :beer2: