After Dylan Bronn's bizarre own goal in extra time handed Senegal a 1-0 victory in a drama-filled semi-final, Tunisia were once more the authors of their own downfall.
Jamilu Collins' cross from the left ought to have been simple for Moez Ben Cherifia to collect, but the goalkeeper collided with his own defender Yassine Meriah, allowing Ighalo to pounce for his fifth goal of the competition.
Besides that, opening lapse in concentration, Tunisia held their own for large periods of the encounter.
Taha Khenissi and Ellyes Skhiri both had chances to equalise before the break but both dragged their efforts wide of the target.
The second period failed to ignite, with the contest slumping into the level of intensity you would expect from a third-place play-off game.
Midway through the second half, Samuel Chukwueze forced Ben Cherifia into a fine one-handed save, but one goal proved enough for the Super Eagles to claim the bronze position.