The Indomitable Lions' hopes of defending their title won in Gabon in 2017 ended in disappointment following a 3-2 loss to the Alexandria Stadium.
Stephane Bahoken and Clinton N'Jie scored for Cameroon but an Odion Ighalo double and Alex Iwobi effort sent Nigeria through to the quarterfinals.
"We started slowly but grew into the game," Seedorf said at the post-match press conference.
"After we went ahead, we settled for 2-1 instead of going for more goals.
"Nigeria have shown that they can score and they did.
"It's been a good tournament. My team has shown discipline which I'm happy with. There's room for growth."
Saturday's loss has cast doubt over the future of Seedorf, who was handed the Cameroon coaching job in August last year.
"Maybe we'll give it a few days," Seedorf responded when questioned about a decision regarding his future.
"Right now I'm sorry for my players for the loss.
"I hope the fighting spirit that we've shown can be carried through into the future."
Until Saturday's reversal, five-time champions Cameroon had not lost a knockout stage game at Afcon since a 3-1 quarterfinal defeat to Angola in 2010.
The three goals conceded against the Super Eagles are as many as they had conceded in their previous nine Afcon games.