The 23-year-old Belgium international suffered the injury in a collision with Aston Villa striker Emile Heskey during Saturday's 2-2 Barclays Premier League draw at the Stadium of Light.
A club statement read: "Sunderland goalkeeper Simon Mignolet underwent surgery [on Sunday] to repair a broken nose. The operation was successful, but he will require further scans to assess the full extent of his injuries."
Mignolet left the field with blood pouring from his nose shortly after the break as substitute Keiren Westwood was handed a league debut for the club. Any extended lay-off for the Belgian could hand the Republic of Ireland international the chance he has been craving to stake his claim for a starting berth.
Mignolet has established himself as number one on Wearside with £9million Craig Gordon plagued by injuries and his contract rapidly running down.
Westwood's summer arrival on a free transfer from Coventry significantly added to the competition, and the 27-year-old proved his worth at the weekend with a stunning late save to deny Sunderland old boy Darren Bent what would have been a winning goal.
Mignolet has started 21 of the club's last 22 games with Westwood's appearance in the 1-0 Carling Cup second-round defeat at Brighton on August 23 his only senior involvement before Saturday.
Manager Steve Bruce will hope the former Sint-Truiden player is not facing a lengthy absence regardless of his confidence in Westwood, however, with injuries severely depleting his resources in the goalkeeping department.
Gordon is not due to resume training after a knee problem until the end of November, while number four Trevor Carson is currently out with a back injury.
Indeed, with Bruce's men due to make the trip to Old Trafford to face a Manchester United side humbled 6-1 by arch-rivals Manchester City in their last home game on Saturday, Bruce has admitted the club may seek special dispensation to sign a keeper on loan if Mignolet is missing for an extended period.
Source: PA
Source: PA