Osimhen, who has been in superb form in recent weeks for the Serie A league leaders, was set to lead the frontline for Nigeria in Cameroon in late January, but a clash of heads while playing Inter Milan on the weekend resulted in surgery and a long layoff.
Napoli said on the their website on Tuesday afternoon: "On Tuesday morning, Victor Osimhen was operated on his cheekbone and eye socket.
"Titanium plates and screws were used in the operation. The player is doing well and will remain under observation for the next few days.
"Osimhen is expected to return to action in three months."
Osimhen faced criticism following his debut season in Italy, as he struggled to live up to the weighty expectations that accompanied his €80 million transfer from LOSC Lille during the summer of 2019.
Injury problems and disciplinary issues didn't help, while a goal return of 10 league goals all term left him under pressure heading into the current campaign.
This season, however, Osimhen has answered critics emphatically.
He's spearheaded Napoli's super start to the season -- as they've established themselves as genuine title contenders -- and had scored five in 10 in Serie A heading into last weekend's showdown with reigning champions Internazionale.