Sexton had a scan over the weekend and has been given the all-clear to face the Pumas, with Ireland team manager Mick Kearney admitting they pulled him out of the 53-0 thrashing of Fiji at Thomond Park merely as a precaution.
"At a stretch, Jonathan could have stayed in the squad on Saturday but it was felt it wasn't prudent and we withdrew him solely as a precaution," Kearney told the Irish Independent.
"It's not even a minor concern to be honest. He received treatment over the weekend and even today there was considerable easing.
"The scan was nothing more than a precaution and it was determined there was no damage. Jonathan was back jogging and will train fully on Thursday and will be absolutely fine for Saturday."
Kearney also confirmed they have no other new injury scares ahead of Saturday's Test at the Aviva Stadium, although Connacht flanker John Muldoon has already been sidelined for around three months after suffering a medial ligament tear.
"There are no serious concerns for Saturday," added Kearney. "Tommy Bowe suffered a dead leg against South Africa and didn't train last week but he is back running and will take a full part in training tomorrow.
"Eoin Reddan jarred an ankle but he has trained and will be fine too."