Wasps were penalised at a scrum 40 metres out with Stephen Myler making no mistake with the crucial kick.
Young said: "It was a hard decision to accept as it was for non-engagement at the first set. It was the first penalty for that offence during the game when there was reset after reset."
Wasps were unlucky losers as they dominated the second half but three missed penalties from Elliot Daly cost them the match.
Young continued: "Nobody expected us to win today; it was a massive challenge against a quality team in a very physical game.
"The players didn't get what they deserved for with 30 seconds to go I thought we were home"
Saints' coach Jim Mallinder conceded his side were fortunate to win the Premiership contest.
He said: "The referee made a couple of close decisions. He made a brave decision at the first scrum and we were lucky it went our way.
"Stephen Myler is steady in those circumstances and kicked very well throughout the game."
Myler was Northampton's hero, kicking four from four penalty attempts and only missing with the conversion of Christian Day's try.
Myler said: "It was tricky out there but I was able to get to grips with it. I just stick to my normal procedures for every kick."
Northampton kept their line intact, which drew credit from Mallinder.
He continued: "Defensively we were very strong but we gave away a couple of penalties for over exuberance.
"Wasps put us under a lot of pressure as we just couldn't get out of our own half.
"It was a massive win for us, away from home just before Christmas but we always knew it would be hard down here as last year we won with a try in the last minute."
George North was very quiet in the centre berth and made little impact on the game but Mallinder said: " George Pisi has been out for six weeks so George North gives us an option as he is happy to move into number 13 - but we see him as a winger."