The Swedish striker was forced off midway through the second half and is certain to miss Tuesday's return fixture at Stamford Bridge, where the French league champions will attempt to defend a 3-1 advantage.
PSG head coach Laurent Blanc said in his press conference on Friday: "Ibrahimovic has suffered a muscle injury.
"He will be unavailable for the weeks ahead without a determined duration.
"Ibrahimovic is a player who scores a lot of goals and brings lots to the team. It's a bad blow for us.
"He will be available for the end of the season."
PSG president Nasser Al Khelaifi had predicted on Thursday, prior to Ibrahimovic undergoing an MRI scan, that the club's talisman forward would be absent for "a minimum of four weeks".