He said: "I was delighted to make my first start today and it is something that will live with me forever.
"It was really tough and a massive step up from the LV= Cup and European games I've been involved in but that is the level you have to reach."
Howard came up against the likes of England captain Chris Robshaw, England scrum-half Danny Care and former New Zealand fly-half Nick Evans.
And he admits that he enjoyed the challenge of facing some of the best players in the world.
He continued: "It was surreal coming up against those players today. I've been trying to stay relaxed this week and not get too nervous.
"But when you think to yourself 'I was at school two years ago and now I'm playing against these international players' you have to pinch yourself."
Warriors led 26-20 at one stage of the match before Harlequins clawed their way back and battled to victory.
And, according to Howard, his side should be pleased with their attacking performance.
He added: "We've tried all year to play a bit more of an expansive game and today we showed what we are capable of going forward.
"We went out there and put our hearts and bodies on the line and if we all do that next season, we will be in a good position."