The injury was sustained in a 4-3 victory against Aston Villa and looks to be a setback of four to six weeks.
Ings had to be taken off in the 85th minute of play after scoring his fifth goal of the season, which happened to be the match winner.
Ralph Hassenhuttl confirmed the injury despite a statement by Southampton soon after the match playing off the severity of it.
The Saints boss said on Wednesday: "At the moment it looks like he is out for four to six weeks.
"He'll have a small surgery tomorrow (Thursday) morning. It could be worse, but he'll be out and it's not good news for us."
Southampton are sometimes overlooked without Ings, but Hassenhuttl insisted otherwise.
"We are more than Danny Ings. It's a big loss but it's important now for other players to give us alternatives.
"Nobody has to play like Danny Ings, every player should play his best possible game."
Ings is also going to miss the next international break where England have their final two crucial Nations League qualifying matches.