Speaking to reporters before this weekend's Belgian Grand Prix, the 24-year-old Briton added he felt remorseful that his behaviour had overshadowed Piastri's maiden victory and the team's merited one-two finish.
"I was a bit silly and didn't think of letting him go earlier," Norris said.
He added he was 'not too proud' of his protracted team orders conversation with his race engineer Will Joseph that resulted in the team finally giving Norris an instruction to 'do it now' after several earlier prompts to do so 'at your convenience'.
"Could it have been handled slightly differently from both a team side and from a personal side? Yes, absolutely," admitted Norris, whose recent form has seen him emerge as the main challenger to defending champion Max Verstappen for the drivers' title.
"We wouldn't be having this conversation now in some ways," he said.
"Whether people on the outside think, and come up with their own stories, of what happened and what I would've done and wouldn't have done. I don't mind about that.
"But it's the things that I could have done… The fact that I clouded over Oscar's race win, his first race win in F1, is something I've not felt too proud about.
"The fact we had a one-two and that was barely a headline after the race -- nothing was really spoken about it from that side -- that's the bit I felt worst about.
"Apart from that, we've discussed it. We've spoken about it. Both sides could have done things a little bit better and a little bit differently. It's almost not good that we had it, but it's a good moment that we've had it. We've learned from it and hopefully it's done better next time."
Asked what he would do differently if he was in the same position again, Norris said: "Just let him pass straightaway. It's such a stupid thing that I didn't because we're free to race.
"I could just let him pass and still try to race and overtake him.
"It sounds so simple now, but it's not something that went through my head at the time," he added.
Norris goes into Sunday's race 76 points adrift of three-time champion Verstappen, who has been leading the championship for a record 52 consecutive races. The Dutchman, however, is without a win in the last three as he seeks his fourth successive victory in the Belgian Grand Prix.
Both Norris and Verstappen have Belgian mothers and expect to have significant support although there is likely to be a much larger contingent of 'orange army' backing the champion.
