The Celtic defender came off early during the Bhoys' Scottish League Cup quarter-final win on Wednesday.
Celtic defeated St Johnstone 1-0 on Wednesday night.
Celtic take on Rosenborg in the Europa League on Thursday.
Scottish Premiership giants Celtic loaned Kristoffer Ajer out to Kilmarnock in 2017 - and have now sent Calvin Miller to Dundee.
Kristoffer Ajer has been at Celtic since 2016.
Celtic defender Kristoffer Ajer is on international duty with Norway.
Three Celtic players that need to improve after the internationals.
Glasgow Rangers goalkeeper Allan McGregor has avoided a ban after the Ibrox stopper kicked out at the defender.
Celtic's Scottish Premiership champion Kristoffer Ajer has a long way to go if he is to live up to former Fulham and Premier League defender Brede Hangeland.
Rangers goalkeeper McGregor was caught kicking out at Celtic's Kristoffer Ajer during Sunday's clash.
Celtic new boy Jack Hendry could be one half of a fine partnership.
Ajer started at centre-back as Celtic progressed to the Champions League group stage despite the loss.
Ajer has barely featured under Bhoys boss Brendan Rodgers and is set to leave Celtic Park in January. Could Leeds United, Queens Park Rangers or Barnsley be the defender's next stop?