Isaiya Katoa is scheduled for ankle scans on Saturday, with Tonga's World Cup campaign beginning in mid-October.
The 22-year-old Dolphins half could miss the tournament if scans show a syndesmosis injury requiring surgery.
A sprain would be the best-case outcome, potentially needing only a few weeks of rehabilitation before Tonga's opening match.
Katoa hurt his ankle in a tackle during the first set of the Dolphins' preliminary final against the Roosters, but played through the remaining 79 minutes.
The Courier Mail reported he could barely walk after the match and was seen in a moon boot on the way to the team bus about 90 minutes after full-time.
Dolphins coach Kristian Woolf said Katoa was in considerable discomfort but continued playing in pursuit of a preliminary final victory.
"I'm not sure if I'll be right (for the World Cup), I hope I am," Katoa told News Corp on Friday night.
"It's pretty sore at the moment and I'll have some scans to see how bad it is.
"I got my ankle twisted in that tackle, I felt it straight, and I just had to get through the game and do the best I could.
"Hopefully it's not too serious and I'll be OK to play for Tonga."