With the Blaugrana leading 1-0 at Camp Nou in the second leg of their last-16 tie the 18-year-old hit the post, and moments later Lionel Messi scored his second goal of the evening.
"I did not feel afraid," Niang told reporters. "I played the same way I do in Serie A, but I lost sharpness because you have to run so hard against Barcelona.
"I thought about it once, but five minutes later I had forgotten it. I hoped we would score after the break, but they are a great team and after the third goal it was all much more difficult.
"The 2-0 from the first leg was not enough to say we were through. Barcelona still would've had to get it wrong and when they are on a night like this, they're tough for everyone. Now we have to stay focused and think about the next game against Palermo."
The draw for the quarter-finals will be held on Friday.