NIGERIA leapfrog the Elephants to go second in Group A and are behind leaders Equatorial Guinea, who beat Guinea-Bissau 4-2 earlier on Thursday, on head-to-head record.
The Ivorians have three points after two games and will now need to beat Equatorial Guinea on Monday (17:00 GMT) to guarantee progress to the knockout stage.
Nigeria – whose four points could already be enough to see the three-time winners through – face Guinea-Bissau (17:00 GMT) in their final Group A fixture.
The newly-built Alassane Ouattara Stadium in Abidjan has now hosted four games in this Nations Cup with several more, including the final, yet to come.
So club managers in Europe and beyond will have been concerned to see multi-million pound players taking part in a contest held on a dry pitch that cut up regularly.
Osimhen’s best opportunity came after just eight minutes when he latched on to a pass from Samuel Chukwueze but the Napoli forward failed to keep a bouncing ball down, sending his effort high over the bar.
Less than a minute later, Nigeria goalkeeper Stanley Nwabali was quickly off his line to use his body to make a point-blank save from Christian Kouame.
Ivorian defender Evan Ndicka then failed to connect properly with a half-volley from near the penalty spot, allowing Nwabali to comfortably gather.
After the fast start, the pace dwindled as the first half wore on, and the deadlock was ultimately broken early in the second period after VAR played its hand.
Diomande’s challenge on Osimhen after 51 minutes was fractionally late, catching the African player of the year and sending him to the turf.
With Osimhen down, the game carried on for around one minute until Algerian referee Mustapha Ghorbal was called over to review the challenge on the monitor.
Having changed his decision, Super Eagles captain Troost-Ekong was the surprise choice to assume penalties duties, with the former Watford defender choosing power over placement to beat Yahia Fofana.
The tournament hosts failed to find a way back into the game, with Seko Fofana and Franck Kessie blazing efforts well off target and Ndicka sending a header from a free-kick wide.
The Elephants’ first ever defeat against Nigeria on home soil means Ivory Coast become the first host nation to lose an Afcon group game in 18 fixtures going back to 2012.