The 22-year-old Denmark international has struggled to make an impact since his £1.2m move from Aalborg last summer but he netted his first goal for Villa in the 2-1 FA Cup defeat to Sheffield United last weekend.
Lambert had little to cheer after that game but Helenius' goal was one bright spot for the Scot with Christian Benteke out of form up front and Libor Kozak ruled out for the season.
Lambert told the Birmingham Mail: "If there is one plus following the Sheffield United defeat it's that I thought Nicklas did well when he came on.
"It was a great goal he scored. He's had a bit of a hard time since he's been here.
''When you are that young and you are trying to get to a level, sometimes people will hit the ground quicker. He's a really lovely guy, a nice guy and it was a good goal so that will do his confidence the world of good."
Czech Republic international striker Kozak had surgery at the weekend after breaking his leg in training before Christmas.
"Everything went well," added Lambert.
"Everybody is quite happy with the operation, so hopefully it is a recovery for him now and get him back. Hopefully he will be back for pre-season."