Victory, which came from a last minute penalty from Xavi Simons, wasn't enough for Spurs as Atletico reached the Champions League quarterfinals 7-5 on aggregate.
Lookman said afterwards: "We're very happy to be into the next round. Every game is hard, and everyone knows the quality in this competition.
"The five goals in the first leg have taken us through, and there are positives to take tonight, so into the next round we go.
"Spurs scored first, and it would have been easy to collapse, but we had the mentality to stay calm, stay in the game and get opportunities. It was nice to be back in London, I call it home.
"Barcelona will be a special, special game against another tough opponent. We need to be ready for it and we'll prepare in the right way. Let's take it as it comes."