Austin, Southampton's top scorer this season with nine goals in all competitions, missed Sunday's 1-0 Premier League win over Middlesbrough after being injured in Thursday's 1-1 Europa League draw with Hapoel Beer-Sheva.
"He needs surgery and will be perhaps between three months and four months [out]," Puel told reporters.
Austin, 27, has been a key figure at the club since joining from Queens Park Rangers in January for a transfer fee of four million pounds ($5.02 million).
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Southampton's home victory over fifth from bottom Middlesbrough lifted Puel's side to 10th in the table.
(Reporting by Neil Robinson; Editing by Tony Jimenez)
