Goals from Victor Moses and Victor Obinna sealed a 2-0 win in the second leg in Calabar on Saturday to send Nigeria through to their fifth FIFA World Cup finals.
Moses' penalty in the 20th minute settled their nerves, but it was not until Obinna's late strike that the celebrations were able to begin.
Keshi admitted his side had not been at their fluent best but was proud they had enough to record the win and end Ethiopia's dream of a first appearance at a World Cup finals.
"The first thing was to make sure we qualified," the 51-year-old said. "Our flag is flying in Brazil, I will take it.
"In today's game I don't mind that we played badly as long as we qualified. We have other games were we can play beautiful football.
"There was a lot of anxiety around the players. Because it's the last game, they wanted to qualify.
"I had to calm them down and make sure their state of mind is intact, but I knew it was going to be a little difficult for them to focus.
"But we had to try to make sure we got them to calm down a bit."
Nigeria have not got out of their group in their past two World Cup appearances, finishing bottom of their pools in both 2002 and 2010.
