Wolves were fortunate to still be in the match at the break after Villa hit the bar twice through Ollie Watkins and Ezri Konsa.
But the visitors were much improved in the second period and a little unlucky not to win, with Conor Coady striking the post and Romain Saiss somehow putting the rebound over the bar from a yard out.
Nuno said: “Everything changed in the second half. Our first-halves not being good and our second halves being better is something we have to improve on.
“Why is it? I wish I knew! It is something we have to reflect on and think, try to find the why and try to stop it.”
“We had good chances and improved in the second half a lot. The first half was not good.
“We weren’t good in possession. We weren’t as close as we should have been. We had little control.”
Coady, who only netted his first Premier League goal in last Tuesday’s 4-1 defeat at Manchester City, was also denied by Villa goalkeeper Emiliano Martinez in the second period.
Asked about what he would be saying to Saiss, following his miss, Nuno replied: “I say what I should say, they he should have done better. But the mistake is something we are supportive of.
“It is no problem. Saiss should be proud because he fought hard for the team.
“It could have been better from Coady. It was a close range header. But credit to him. It is something we are pushing, for him to go in the box more.”