The 30-year-old, who played for Watford before moving to China two years ago, has scored three goals at the African football showpiece in Egypt.
That tally gives him a share of the lead in the Golden Boot race with Senegalese Sadio Mane, Congolese Cedric Bakambu and Algerian Adam Ounas.
Two of his goals came in the 3-2 second round defeat of defending champions Cameroon, and he could have finished with four having hit the woodwork and been foiled by a superb save.
A few hours after Nigeria triumphed last Saturday, South Africa stunned hosts and pre-tournament favourites Egypt 1-0 in Cairo with Thembinkosi Lorch snatching a late winner.
Most South Africans had written off Bafana Bafana after a dismal one-win group campaign and were discussing who should replace unpopular coach Stuart Baxter.
If Nigeria and South Africa can replicate their last-16 form, a titanic struggle for supremacy is on the cards at the Cairo International Stadium.
Ighalo says the 2-0 group stage loss to outsiders Madagascar was a massive wake-up call that worked in favour of the Super Eagles.
"Any thoughts we had of an easy passage to the closing stages vanished after that defeat. We realised that many teams were motivated by playing Nigeria and raised their game against us.
"While I have enjoyed scoring three times in Egypt, it is irrelevant who puts the ball in the net as long as he is a Nigerian.
"We want to win the title a fourth time, but South Africa also want to get their hands on the trophy, as do all the other title contenders."
South Africa have consistently battled against Nigeria, with a shock 2019 Cup of Nations qualifying triumph in Uyo their lone competitive victory over them.