The ex-Borussia Dortmund boss took a year out from coaching after leaving Signal Iduna Park, returning to football in May 2018 when he signed a two-year deal at PSG.
The 45-year-old has since set a new club record by winning each of his first six competitive matches in charge of the Ligue 1 champions, the last of which being a 4-0 victory over Saint-Etienne at the Parc des Princes on Friday.
Tuchel told L'Equipe that the offer to take charge of the German champions arrived too late to tempt him, saying: "With Bayern, there were only contacts.
"Their proposal arrived too late, I had already decided to join the PSG.
"My choice after Dortmund was very clear, it was something I had deep down inside me - if I'm lucky enough to have an experience abroad, I have to try. "It was clear with my family, my staff and for me. Paris was special, it was a nice surprise."
Napoli and Red Star Belgrade are the French club's other opponents in Group C, and Tuchel said his players must focus on the group stage rather than picturing themselves in the knock-out phase of the competition.
"The Champions League is not just a tactical competition, it's more a generational competition," said Tuchel.
"Real Madrid has a generation that knows how to win big matches, how to resist the pressure.
"For me, we must reverse things. If we work well every day, if we live well every day as a group, we should be ready for the big matches.
"And if we do not focus too much on these big games to come in February, maybe we can better address them.
"Today, we have to focus on group matches, because we have a very strong group."