The 31-year-old midfielder suffered the injury during stoppage time in the African team's 2-0 win over Iceland on Friday, reports Xinhua news agency.
"Unfortunately our captain has a fracture but I think he will be able to play with a splint," Nigeria coach Gernot Rohr said in a video published by the Nigerian football federation on Sunday.
"Our medical team is looking after it," he added.
Nigeria will progress to the round of 16 if they win Tuesday's match in Saint Petersburg. A draw will also see them advance if Croatia beat Iceland.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
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