Manchester City forward Iheanacho had other ideas, winning and converting a penalty in the 81st minute to earn a share of the spoils for Salisu Yusuf's side, who will have been concerned at the site of Ogenyi Onazi departing with a potentially serious injury early in the contest.
Nigeria may also have been unsettled before kick-off, amid reports Leicester City winger Ahmed Musa resigned as vice-captain in the lead up to the game.
Perhaps as a consequence, Senegal started strongly, Sow hitting the post early on from close range, while Cheikh Ndoye also called Nigeria goalkeeper Daniel Akpeyi into action with a header from Idrissa Gueye's corner.
Nigeria received a blow in the 25th minute, when Onazi was stretchered off injured, to be replaced by John Ogu.
It took until just before half-time for Nigeria to enjoy their first real opportunity of the match through Iheanacho, the pacey forward somehow failing to hit the target with a low effort from almost point-blank range.
Senegal broke the deadlock nine minutes into the second half, Everton man Gueye crossing from the right and Sow on hand to score with a right-footed finish from inside the area.
Former Aston Villa midfielder Gueye almost went from provider to scorer moments later, poking just wide with his left foot.
The Senegal fans at The Hive Stadium got what they wanted with just over half an hour remaining, when star Liverpool forward Sadio Mane was introduced by head coach Aliou Cisse.
But it was Nigeria's supporters who were celebrating late on, as Iheanacho atoned for his earlier miss by converting from the spot to level the scores with nine minutes to go after being fouled by Senegal shot-stopper Pape Ndiaye.
Both teams are in friendly action again next week, with Nigeria's next match back in Barnet against Burkina Faso on Monday, while Senegal are due to tackle Ivory Coast in Paris on the same day.