The 22-year-old £6million signing scored Blackburn’s first goal in the game four minutes before the break.
“£6million for a frontman is a drop in the ocean today,” said Allardyce.
“We decided to go young and invest in someone who can get better and better.
“Niko has come through and said ‘I’m worthy of a place in the side’.
“You could see his quality today. I’m delighted for him and I’m delighted for everyone.”