The Brazilian, who arrived from Real Sociedad in January ahead of a possible permanent deal in the summer, finally ended his drought to seal victory against Sheffield United at Molineux.
He calmly tucked away Adama Traore's cross to break his duck in his 13th appearance, while Wolves moved to 41 points with six Premier League games remaining.
And Nuno said: "It's very important. Willian joined us and in a short period, he was in the team and was playing, not knowing his team-mates.
"It's been hard work to try to get these complicities together, and he's showing the work he's been doing.
"He leads the game. He drops and helps the team.
"The goal will boost his confidence, for sure."
It was an underwhelming performance on the whole, but Wolves sealed back-to-back wins.
The Blades, meanwhile, have now had their relegation to the Championship confirmed.
"We faced a Sheffield team that I have huge respect for," said Nuno.
"I have huge admiration for that group of players. For Chris Wilder, for Paul Heckingbottom, because we started together in the Championship. For sure, they will react and bounce back.
"Regarding the match, it was two different halves. The first half was not so good. The second half, we started better and achieved the goal.
"We then dropped too much and allowed Sheffield to have control, but we also should have killed the game with our counter-attacks."
Wolves are currently 12th in the table, and on if a top-half finish is the aim, Nuno added: "It's not about the table.
"It's about how we finish, how we do things and how we build for next season.
"We have a tough game next weekend. The performances need to improve and the players need to engage until the end.
"It's about building and improvement. It's always been like this and it will never change."