The 20-year-old is due back in Leicester on Tuesday but will now be sent for scans after pulling up while playing for Nigeria.
He was forced to limp off during the 1-0 victory over Zambia on Saturday, with the coaching staff unwilling to take a risk with him.
His performance helped Nigeria secure their spot at the World Cup finals but Ndidi now faces a race against time before returning to club duty.
Leicester will be boosted by the fact they do not play until Monday, when they take on West Brom.
However, any injury will derail Craig Shakespeare’s plans, with a number of players still out injured.
Andy King, Vicente Iborra and Daniel Amartey are the only fit midfielders, with Matty James out and Adrien Silva still unable to play after his transfer was blocked by FIFA.