Former Continent's Best Player of the Year the Napoli star was instrumental in Nigeria establish a 3-0 lead, before they were forced to defend resolutely for a narrow win.
The three-time champions survived a stunning comeback attempt from their opponents to progress to the knockout stage of the Afcon tournament taking place in Morocco.
The Super Eagles appeared to be in complete control in their pool clash in the Moroccan city, holding a 3-0 cushion with only a quarter of an hour remaining courtesy of strikes from Victor Osimhen, Wilfred Ndidi and Ademola Lookman.
Yet, a Tunisian defender pulled one back with a close-range finish from a Hannibal Mejbri free-kick, sparking hopes of a turnaround.
The drama intensified when Tunisia were given a spot-kick after a VAR review identified a handling offense by the Nigerian defender. The left-back converted in the 87th minute to set up a frantic conclusion.
The Carthage Eagles were inches away from a last-gasp equalizer in stoppage time, with their skipper heading a chance just past the post before a substitute guided a half-volley past the goal frame.
This result ensures that Nigeria, winners of the competition on 3 previous occasions, move to 6 group points and are guaranteed first place in their pool with one game left to play.
For the round of 16, they will face a third-placed side from one of Group A, B or F.
In the other match, the 2004 champions remain on three points, with Uganda and Tanzania tied on one point each after registering a 1-1 draw in the day's other fixture.
The concluding group fixtures will see the group leaders stay in Fes to play Uganda on Tuesday, while the Eagles of Carthage return to Rabat to confront Tanzania.
Ali Abdi drilled home from the penalty spot to offer Tunisia a glimmer of hope of snatching a point.
Nigeria, runners-up in the previous edition, are the second nation after Egypt to reach the next phase, but their manager and fans will certainly be feeling relieved.
What seemed set to be a straightforward last period morphed into a nerve-wracking conclusion.
The prolific striker had a effort ruled out for an infringement before breaking the deadlock right before half-time, precisely placing a glancing effort into the far post from an Ademola Lookman cross.
The lead was extended early in the second period when the Leicester City midfielder climbed above everyone to thump in a powerful nod from a Lookman corner.
Osimhen then set up his teammate for the seemingly decisive goal, only for Montassar Talbi to direct a header past the Nigerian shot-stopper to initiate the comeback.
The key moment came when a high ball struck the forearm of Bright Osayi-Samuel, with the official pointing to the spot after consulting the VAR monitor.
Despite the defender's successful penalty, Tunisia ultimately fell short of completing a remarkable comeback.
Tunisia's destiny is still in their own hands; a draw against Tunisia will be sufficient to secure progression, and manager Sami Trabelsi will be keen to prevent a repeat of the 2013 early elimination that resulted in his departure.
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