Rovers dominated Wednesday's goalless draw at home to Hibernian but failed to put away the numerous chances they created.
Aside from the four goals they put past Cambridge in their first friendly on July 14, Blackburn have scored five in four full games and two 45-minute run-outs.
The forward line will be boosted by the arrival of £6million Croatia international Nikola Kalinic, assuming he obtains his work permit at a hearing next week, but Allardyce has told his current strikers they cannot afford to waste chances.
"If you are a finisher you have to finish them," he said.
"It is a bit of worry but the good thing is they are creating chances.
"We know we are not going to score a lot of goals in the Premier League because we don't spend the money on strikers like everyone else does.
"That usually determines what position you finish in the league but if we get two strikers who score 10 or more we will finish in the top half or better.
"If we don't we will finish in the bottom half and if we miss a load and they only score three or four we will struggle.
"That is the difference between putting the ball in the back of the net or not."
Allardyce has brought in Chelsea's Franco Di Santo on loan until January to add competition up front and is confident the 20-year-old Argentinian will adapt quickly after getting few opportunities at Stamford Bridge.
"He has good movement, he has a nice touch, he is good in the air," the Rovers boss told the Lancashire Telegraph.
"As time goes on and as he gets more used to the players he is playing with and more used to the Premier League, with a few more starts than he got at Chelsea, then he will show some really good things.
"With regards Nikola Kalinic, we are waiting for a work permit. If we get that that's fine, if we don't unfortunately there won't be a deal, so we will keep our fingers crossed."