Ex- African Footballer of the Year the Napoli star was instrumental in Nigeria build a 3-0 advantage, before the Super Eagles were compelled to defend resolutely for a hard-fought victory.
Nigeria survived a dramatic late rally from Tunisia to advance to the knockout stage of the Afcon tournament taking place in Morocco.
Jose Peseiro's side appeared to be cruising in their pool encounter in Fes, enjoying a 3-0 lead with just 17 minutes left courtesy of strikes from Victor Osimhen, Wilfred Ndidi and Ademola Lookman.
However, a Tunisian defender reduced the deficit with a close-range finish from a Manchester United midfielder set-piece, sparking hopes of a turnaround.
The tension escalated when Tunisia were given a spot-kick after a video assistant referee check spotted a handball by the Nigerian defender. The left-back converted in the dying stages to create a frantic finale.
Tunisia came agonizingly close from a last-gasp equalizer in added time, with captain Ferjani Sassi heading a chance narrowly wide before a substitute guided a bobbling volley past the goal frame.
The victory means that Nigeria, champions of the competition on three past instances, advance to 6 group points and are guaranteed top spot in Group C with a match left to be contested.
For the round of 16, they will face a third-placed team from either the other preliminary groups.
Meanwhile, the 2004 champions remain on three points, with the East African teams tied on a single point each after registering a one-all stalemate earlier on Saturday.
The concluding pool matches will see Nigeria stay in Fes to take on Uganda on the next matchday, while Tunisia travel back to Rabat to confront the Taifa Stars.
The Tunisian defender drilled the ball from the penalty spot to offer his team a glimmer of hope of snatching a point.
Nigeria, finalists in the previous tournament, are the next team after Egypt to qualify for the next phase, but coach Eric Chelle and fans will undoubtedly be feeling relieved.
What looked like set to be a comfortable final quarter morphed into a tense conclusion.
Victor Osimhen had a effort ruled out for offside before opening the scoring on the stroke of half-time, precisely placing a glancing effort into the bottom corner from an Ademola Lookman delivery.
The lead was doubled soon in the second half when the Leicester City midfielder rose highest to thump in a header from a set-piece kick.
Osimhen then set up Lookman for the seemingly decisive goal, before Montassar Talbi to steer a powerful header past the Nigerian shot-stopper to begin the comeback.
The pivotal moment came when a high ball struck the arm of Bright Osayi-Samuel, with the official pointing to the spot after reviewing the pitchside screen.
Despite the defender's confident conversion, Tunisia ultimately came up just short of pulling off a remarkable comeback.
Tunisia's destiny remains in their control; a draw against Tunisia will be enough to secure progression, and manager Sami Trabelsi will be keen to prevent a repeat of the past early elimination that resulted in his departure.
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