The world's most expensive player has been out of action with the problem since the win over Montpellier on February 1 and could miss Saturday's game against Amiens.
But Tuchel insisted that Neymar would be fit for the clash at Signal Iduna Park.
"Whether or not he plays on Saturday (against Amiens), he will be in Dortmund, I'm sure of it, but without being in the best shape he was in two weeks ago," said the former Dortmund boss.
"But he will help us. I am sure and convinced of that."
Neymar missed last season's surprise Champions League last-16 defeat by Manchester United with a foot injury, and also sat out the second leg of the loss to Real Madrid at the same stage of the competition in 2018.
PSG have still not reached the Champions League semi-finals since their Qatari owners took over in 2011.