The Munster fly-half's availability for England's visit to Dublin on February 24 is not in doubt but coach Eddie O'Sullivan revealed he will be rested this week as a precautionary measure.
O'Sullivan said: "Ronan had an ankle problem. We don't what happened because he finished the game.
"He must have gone over on it late in the match because he has no memory of it happening. It was a little bit sore after the game.
"We iced it and he was walking around OK but then last night at the meal it swelled up quite a bit.
"We're confident it's just a knock and nothing sinister. The swelling has gone down and it's a lot better.
"But it's sensible not to put any pressure on it so he won't be training this week."
Skipper Brian O'Driscoll and scrum-half Peter Stringer, who missed the clash with hamstring and hand injuries, will also return to training next Monday.
O'Sullivan said: "Brian and Peter will be fine for England. Time was against them for France but England won't be a problem - unless something unforeseen happens.
"The plan for both of them is that they'll take full part in training next Monday. This week they'll continue their rehab."