The in-form striker, who plays for Saudi side Shabab, scored with a trademark header to set Angola on their way to a 2-0 victory over Malawi.
It was his third goal in the tournament, having scored twice in Angola's 4-4 draw with Mali in the opener last Sunday.
He was carried off on a stretcher in the second half after picking up an injury, making way for Benfica striker Mantorras.
"I'm yet to know the extent of the injury, but I will play against Algeria," Flavio, who left Egyptian champions Ahli in the close season, told Al-Jazeera after the game.
Angola's victory put them on top of Group A with four points, one ahead of Algeria and Malawi.
Mali, who slumped to a 1-0 defeat to Algeria earlier on Thursday, lie at the bottom on one point.
A draw for Angola against Algeria, who qualified for this year's World Cup, on Monday will be enough to send them to the quarter-finals.
"A point will help us qualify for the next round, but we will play to win," Flavio added.