Amid growing speculation over an imminent departure, sections of the Parc des Princes aimed derogatory chants towards Neymar before and during the match.
"It's a little difficult, I don't know what to say. I saw [the public's reaction on Neymar] on my colleagues' phones because I hadn't heard that during the game," Tuchel said about the chants directed at Neymar.
"Can I understand that? Yes and no, that's the way it is in our lives. The emotions are serious, the emotions are still there, okay. But on the other hand, Neymar is still our player, still my player, and I will always protect my players. He's in the locker room, he's here and I'll protect him.
"I can understand that not everyone likes what he said and what he did. I understand, but we have to express a level to express our emotion."
Asked if PSG missed Neymar against Nimes, Tuchel added: "He is still missing, because he can find solutions that only he can find. He can open spaces with movements, accelerations, one against the other.
"It was a little lacking today to be more decisive in the first half. But we have to find other solutions, we have to give rhythm with passes, with intensive runs. But it's clear, he's Neymar, and he has extraordinary qualities. If he is not on the field, he is missing, but it is our challenge to find solutions. We still have to improve."
While Neymar was absent on Sunday, Edinson Cavani, last season's top scorer Kylian Mbappe and Angel Di Maria led the way for PSG in Paris.
After Cavani broke the deadlock via the penalty spot in the first half, Mbappe and Di Maria put the result beyond doubt following the interval.
"The best thing is that they [Neymar and Mbappe] play together," Tuchel said. "It is not a question of whether Mbappe can give more when Neymar is not there.
"Kylian gives a lot, he's been very focused for four weeks now. He puts a lot of intensity into training, into matches. It's great for the team to improve. But the best thing is that Neymar is next to him."
Mbappe, who hinted he could be ready for a "new project" following the 2018-19 season, scored a Ligue 1-high 33 goals as PSG retained their crown last term.
"As I said last year, he is invited by the club to take more responsibilities every day. Taking responsibilities does not mean taking every penalty, hitting every corner or every free-kick," Tuchel continued. "It's not like that, there are many ways to take responsibilities, and he does that.
"He started this season with a lot of concentration, I'm very happy. He's here, I have a feeling he's happy. He has objectives for himself and the team, and he does everything to achieve them. He gives his opinion, and we're going to keep developing that. He has a good relationship with everyone, he is reliable."