In a tournament that has seen a number of the big names fall to shock exits, the Super Eagles are now favourites to lift the trophy ahead of their last-four clash on Wednesday.
However, while the Nigeria squad flew to Bouake on Monday, Osimhen remained in the capital Abidjan with a member of the medical staff, and it remains to be seen whether he is fit to join up with his team-mates ahead of the AFCON showdown with South Africa.
A Super Eagles statement on Monday read: "Members of the team traveled from Abidjan to Bouaké today via a 10pm Air Cote D'Ivoire flight.
"Osimhen did not however make the trip as a result of an abdominal discomfort. Team medics confirmed that he has been placed under close watch with a member of the medical team staying behind in Abidjan with him.
"If cleared by tomorrow morning, he will join the rest of the squad before 5pm."
On Tuesday, he did get the green light to link up with the squad however the exact nature of his injury remains somewhat uncertain.
Napoli striker Osimhen was stretchered off in stoppage-time of the 1-0 quarter-final win over Angola.
The 25-year-old has played in all five of Nigeria's matches at the tournament, though he has not scored since netting the equaliser in his country's opening match against Equatorial Guinea.
The Super Eagles are bidding to win AFCON for a fourth time, having failed to reach the final since they last won in 2013. In the four tournaments that have followed, Nigeria have twice failed to even qualify, and two years ago they were beaten in the last-16 by Tunisia.
Victory over South Africa on Wednesday would set up a final against either hosts Ivory Coast or DR Congo on Sunday.