The flanker's initial X-ray proved positive and he was kept overnight in Cork University Hospital, pending further medical examination today.
Munster Rugby issued an update this evening via their Twitter page that the 30-year-old forward has received 'good news'.
The tweet confirmed: "Niall's injury is not as serious as first thought. His scan today gave him the all-clear so he will just take it easy for the next week."
Meanwhile, the province's head coach Rob Penney rued missed chances when he reflected back on their performance against the league's second-placed team.
Speaking after the 13-6 reversal in Cork, he said: "In those conditions when the opportunities arise, you've got to take them. We probably had two clear try-scoring opportunities in the first half that we didn't nail.
"We got a bit frustrated at scrum time and we lost our way a little bit there and that really cost us too.
"I think a large degree of it was our own problem. You've got to be smart enough to be able to read what the referee's interpretations are going to be. And he was relatively consistent. So we've got some work to do there."
Just before the break, Munster looked to have scored a try through Ronan's placement CJ Stander that could have proved crucial, but Penney was not using that as a straw to clutch at.
"The people that matter didn't think it was (a try). We'll have to revisit it and have a look maybe but it was hard to tell," admitted the New Zealander.
Ronan's injury afforded Penney the opportunity to introduce South African recruit Stander and he was happy with the newcomer's first outing in red.
"He did well. I mean at times it was hard to identify who was doing what and to whom. But he contributed a great deal to the effort.
"I thought there was some good endeavour and good effort going into those terrible conditions in the second half."