Haaland suffered the setback during City's FA Cup quarterfinal win against Bournemouth.
The Norway striker failed with a penalty, though also scored before being forced off on 61 minutes.
City announced last night:
"Manchester City FC can confirm that Erling Haaland has suffered an injury to his left ankle.
"The Norwegian striker sustained the injury during Sunday’s FA Cup quarter-final victory away at AFC Bournemouth.
"Erling underwent initial tests in Manchester on Monday morning and will now seek specialist consultation to confirm the full extent of the injury.
"Assessment remains ongoing to ascertain a full prognosis. The expectation is that Erling will be fit in time to play a further part in the remainder of this season, including this summer’s FIFA Club World Cup."