The 24-year-old moved to Upton Park on a permanent deal from Liverpool in the summer for a reported £15m on a six-year deal.
The ex-Newcastle United striker initially suffered an Achilles injury on the final day of last season, but a fresh problem has marred the start of his campaign, with reports claiming that the forward could be sidelined for the rest of the year.
"It's devastating for Andy and ourselves," Allardyce told Sky Sports News. "It's not frustrating, it is devastating. What we have to do is make sure we treat him in the right manner as quickly as we possibly can again and get it right as quickly as we can.
"It is certainly not as serious as last time, that is the one encouraging thing but hugely, hugely disappointing for him and for us."
Carroll spent a season-long loan with the Hammers last season before joining the club permanently.