Ronaldo went off in the first half of the Euro 2020 qualifier with an apparent hamstring injury. The match ended 1-1.
"I'll know more in 24 or 48 hours," he told reporters.
"It happens, it's football. If you go out in the rain you get wet ... I'm calm, I'll be back in one or two weeks."
A long absence would be a blow to his club Juventus, who signed Ronaldo last year to boost their chances of winning the Champions League. Juventus travel to face Ajax Amsterdam in their quarter-final first leg on April 10 with the return six days later.
Both Ronaldo and coach Fernando Santos said the referee had apologised to them for not awarding a penalty to Portugal
for handball in the second half.
The referee initially gave the spot kick but then changed his mind. VAR is not used in the Euro 2020 qualifiers.
"It was very clear, the referee should have given it," said Ronaldo. "The linesman was 40 metres away so it seems a bit strange."
Santos said: "We saw the incident in the dressing room afterwards and neither we nor he had any doubt -- it was a penalty... He apologised."