An FIA spokesman said the Spaniard had apologised for his conduct and would make up for the breach, in a manner to be determined.
Formula One has cracked down on swearing in press conferences under the leadership of Emirati Mohammed Ben Sulayem, with stiff sanctions set out in the FIA's sporting code.
From this season, a first offence triggers a 40,000 euro fine, rising to 80,000 for the second. A third breach brings a 120,000 euro fine with a one-month suspension and deduction of championship points.
Sainz swore in an FIA press conference on Thursday while discussing a 20,000 euro fine, with half suspended, received at the Japanese Grand Prix last weekend for being late to the pre-race national anthem.
He had explained the lateness by saying he had a "stomach issue" and had to go to the toilet.
"I don’t know if I’m going to get another fine for saying this, but shit happens. It’s the way it is. It’s the way it goes sometimes," he said.
The FIA delegate, who was in the room, said on Thursday he would speak to Sainz before taking any further action.