Helene Elliott reported via Twitter that agent Pat Brisson said Kopitar would have tests in the next day or two but the player doesn't believe the situation to be serious.
"It’s very minor," Brisson told the newspaper. "Whether that means [he's out] a week, two weeks or 10 days, I don’t know."
Kopitar, playing for Mora in Sweden, reportedly left Saturday's game with the injury.
Kopitar had 25 goals and 51 assists (76 points) in 82 regular-season games for the Kings last season. He led all players in the Stanley Cup Playoffs with eight goals, 12 assists and a plus-16 rating as the Kings won their first championship.