Coman's goal at the Parc des Princes came three years after he scored the winner for Bayern in the final against PSG in a virtually empty pandemic-era stadium in Lisbon.
He spent his early years at PSG before joining Italian giants Juventus in 2014 and was transferred to Bayern a year later.
"It was hard to celebrate here, I grew up here," Coman said of his muted gesture after scoring, hands in the hair in an almost apologetic gesture.
His second-half volley squirmed under the body of PSG goalkeeper Gianluigi Donnarumma.
"(My goal) was something we work on in training and I got it just right," Coman said.
"A victory away from home is always good, we could have had more but in the end we were delighted with 1-0," he added.