TheGirl
My son did go skiing in Italy. He was well on his return and our school did not send all pupils home to self isolate (though we later found out some did and were tested).
Then his brother had a cold this week but it was just a cold (and he's asthmatic so I was more cautious than usual). If he'd been coughing, had a fever and had breathing issues, then that would have set my alarm bells off.
Just keep an eye on him for any changes, plenty of fluids and some paracetomol if needed and try not to worry. Lots of normal bugs and colds doing the rounds.