The 21-year-old's 83rd-minute strike proved to be the difference between the two teams at Estadio Do Dragao.
"It was a difficult game," he is quoted as saying on UEFA's official website. "In the first half we couldn't convert our chances. We did in the end and it was very important.
"I tried to score many times and thank God the last one went in. We knew they had a lot of good players, but we were far better tonight.
"We are very strong, but must take things step by step."
In the other Group A game on Wednesday, Dynamo Kiev defeated Dinamo Zagreb 2-0 at home.