Neymar was apparently injured after missing a shot five minutes into the game.
Meanwhile, France World Cup victor Mbappe, left the pitch with what looked to be a shoulder injury.
After the forward was sent through on goal, Uruguay goalkeeper Martin Campana rushed off his line to win the ball cleanly off the teenager's feet.
The Spanish champions have reportedly begun "Operation Neymar", making contact with the player in order to convince him to start pushing for a move away from PSG.
A statement on the club's official wesbite read: "Neymar Jr and Kylian Mbappe have undergone medical examinations today that confirmed: for Neymar an elongation of the right adductors".
All four sides could still qualify for the knockout phase from Group C. Liverpool have the same number of points as leaders Napoli, while PSG sit third, one point behind Liverpool and one point ahead of Red Star Belgrade.
"He came off complaining of pain", said Lasmar.
But he was booed from the field after just six minutes as he hobbled off down the tunnel, replaced by match-winner Richarlison. "(He) will need a little more time for a better evaluation, an image exam, but at first it is nothing important".
France won thanks to Olivier Giroud's 52nd-minute penalty.
The Ligue 1 leaders return to action this weekend against Toulouse but it's their following game, against Liverpool in the Champions League, which they will be most concerned about.