The striker, signed from Monaco last summer, opened the scoring at Loftus Road on Saturday.
Riviere – who hadn’t found the net in 21 previous Premier League appearances – took a punt forward from Tim Krul down with his left foot and shot past Rob Green with his right foot.
But second-half strikes from Matty Phillips and Leroy Fer gave Queens Park Rangers a 2-1 win – and left Newcastle deeper in relegation trouble with one game left to play.
“I’m disappointed because my goal didn’t give the team a win,” said Riviere. “The most important thing for me is that the team gets points.
“For the next game, it gives me confidence. I’ll try to help the team.”
Riviere admitted 17th-placed Newcastle – who must beat West Ham United at St James’s Park on Sunday to be sure of Premier League survival – never got to grips with the tactical changes made by QPR at the break.
“We had a good first half, and after QPR changed tactics, fought well and scored two goals,” said the 25-year-old.
“QPR changed with a 4-4-2 and we didn’t quickly enough change our tactics. We have to focus so that can never happen again.
“We have to keep fighting for the next week.
“It’s a final now for us (against West Ham). Hull have lost and we have to win to stay in the Premier League.”
“It’s massive. We have to win to stay in the Premier League.”