Messi missed PSG's last two games before the international breakÂ with a combination of knee and thigh issues and has yet to score in Ligue 1, where he has been limited to just five appearances.
The six-time Ballon d'Or winner returned to action as a substitute in his country's 1-0 victory over Uruguay. He then started the 0-0 draw with Brazil that helped Argentina clinch qualification for Qatar.
"I'm doing well, otherwise I wouldn't have played," Messi told Argentina's TyC Sports network after the Brazil game.
"It's not easy to play a match with as much rhythm as this one. I know that bit by bit I'm going to step it up. I hope to be able to finish the year well."
Messi could feature for PSG at home to Nantes on Saturday, unless Mauricio Pochettino decides to keep his compatriot fresh for the trip to Manchester City next week in the Champions League.
His first goal for PSG came in a 2-0 win over City in September, and a second victory over Pep Guardiola's team would likely earn them first place in the group.
Before that the league leaders host a Nantes side managed by former PSG defender and coach Antoine Kombouare, who masterminded a shock win last March at the Parc des Princes.
"It's time to change the focus because I still have a lot of desire to continue fighting to achieve the goals that we set here at PSG and I want to stay focused and working to achieve it," Messi wrote on Instagram after landing back in Paris on Wednesday.
"There is only a month and a half left until 2022 and I would like to finish this year in the best possible way and with more good moments that we can achieve in France."
Monaco host Lille on Friday in a meeting of two clubs who have failed to replicate their form from last season, while second-placed Lens go to Brest.
Nice visit Clermont on Sunday before the clash of the weekend between Lyon and Marseille.
Player to watch: Gaetan Laborde
The league's joint-top scorer with eight goals this term, Rennes forward Laborde faces a reunion with the club with whom he began the season as Montpellier travel to Roazhon Park on Saturday.
Laborde scored three times in four games for Montpellier before joining Rennes for 15 million euros ($17 million) just before the transfer deadline.
He hasn't slowed down since arriving in Brittany, bagging another five goals in Ligue 1 for his new side who have won seven of their last eight matches in all competitions.
Standout matches today