The 24-year-old had netted a first-half brace in a 3-3 draw against Royal Excel Mouscron before he was replaced by Youssoufou Niakate at half-time with a suspected knee injury after an opposition player fell on top of him.
"It's a shame that I could not finish the game, a player fell on my knee and it was better to take no chances," Tau said after the match.
"We'll see after the exams [medical], but you know, I do not have to think about playing in the Nations Cup.
"I can hurt myself in training anytime," he added.
Despite not being able to continue with the game, Tau appeared to be walking comfortably as he left the field.
Earlier in the evening, the former Mamelodi Sundowns man paraded his Proximus League Player of the Year gong which he picked up at the league's award ceremony earlier in the week.
"I just want to say thank you to this audience and my teammates," Tau told a packed Stade Joseph Mariën.
"I see this title as a collective award. Thank you all.
"The evening would have been more beautiful with the victory," he explained.
Meanwhile, Tau, who is on loan from English Premier League side Brighton and Hove Albion, admits that his future is still uncertain.
"I do not know yet, I do not think about it, I want to finish the season first, if I'd like to stay, yes, it's a big club," he concluded.
Tau's South Africa have been drawn into Group D at the Africa Cup of Nations, which kicks off on June 21 in Egypt.