Olsson was substituted after just 19 minutes of the 3-0 defeat at Deepdale but Allardyce still expects the 22-year-old Swede to play a full part in this month's pre-season tour of Australia.
Allardyce told Sky Sports News: "It felt a little bit achy and then got worse instead of disappearing, so we brought him off as a precautionary measure.
"Hopefully it'll be just a few days to recover from that and he should be fine for Australia."
Rovers face games against Rangers, AEK Athens and host club Sydney FC in the Festival of Football Tournament Down Under.
They then return to Britain and play a friendly at Hearts before beginning their Premier League campaign at home to Everton on August 14.
Allardyce hopes by then to have brought in more forward firepower to bolster his existing options.
He added: "When you haven't got as much money as everyone else, it makes it difficult to find the right player to make an impact for you.
"It is not a striker we are looking for to make the numbers up, it is a striker we are looking for to make an impact by challenging Jason Roberts and Niko Kalinic. That is extremely difficult for us at the moment."