Nogwanya sustained the injury in the opener against Sweden where she played only 40 minutes of the first half – in her first Olympic Games - before she was substituted by Linda Motlhalo.
She will play no further part in the tournament following advice from the medical team after she underwent scans.
Nogwanya’s withdrawal from the squad means head coach Vera Pauw will be forced to make changes to her starting line-up when they face China on Saturday at the Olympic Stadium in Rio de Janeiro.
The Women’s Olympic Team will have their final training session later today ahead of their encounter with a China side who lost 3-0 to Brazil.
Banyana Banyana goalkeeper Roxanne Barker believes this is a match they have to win to stay in contention for the next round.
“We did really well against Sweden but we were gutted to concede that goal. The only positive is that the performance on that day will surely give us the needed boost to face China with a lot more confidence," said Barker.
"I think what we did against Sweden has made people now realise that South African Women’s football is on the rise and that’s thanks to all the good preparation we had over the last few months.
“We know our capabilities, we know our strengths and we showed that we can mix it up with the best. While all the matches are very important, the upcoming one with China becomes even more important as we did not get any points in our opener.
"We know we deserved something from that match, but it is now behind us and we have to look forward with renewed energy to our next assignement to make sure we get positive results so that we stay in contention for the quarterfinals.
"All is not lost, but we have to work extra hard to win because a loss is unthinkable. Also we don’t want to go to our final match against Brazil needing points desperately.”
The match against China kicks off at 19h00 local time (midnight SA time) with Banyana's final group game coming against Brazil on August 9 in Manaus.