The fan allegedly attacked Burgess with a flag, and came forward after the match, with the Penrith club saying “appropriate action” had been taken.
A statement read: “The club has spoken to several people who may have witnessed the alleged altercation, and has reviewed camera footage from the night.
“The fan has unreservedly apologised for causing any harm to the NRL and the Panthers.
“They have also offered an apology to Sam and the South Sydney club.”
The incident prompted a tweet from Burgess’ mother, Julie.
It said: “Would love to meet the woman (I’m being kind) who hit Sam with a stick as he was leaving the pitch. Sorry Penrith people but that’s not OK.”