This is the second consecutive Afcon the Super Eagles will be missing since winning the 2013 Afcon.
The Super Eagles failed to qualify from their qualifying group, losing the only spot to Egypt.
That was the second consecutive miss the Super Eagles will be missing since winning the 2013 Afcon.
Ighalo believes it will be more painful when the tournament kicks off on Saturday, January 14.
"I felt bad - not just me but Nigerians as a whole are not happy," the Watford striker to BBC Sport.
"Seeing teams playing in the Nations Cup and you see yourself at home you know you're not going to the Nations Cup that's when I' m going to feel bad.
"You know you don't have to dwell on that, we don't have to kill ourselves about that.
"We have to work towards the next one and keep pushing hopefully we will qualify."
The Super Eagles have won the Afcon title three times.