What should I doooo??!!

Hey you guys sooooo... I’m 20 and I’m a college student me and my best friend stay together. I’ve been going with my bf a year and... his parents and his immediate family has to get tested for COVID he hasn’t been around them so he’s stranded so he’s been staying with me 4 days now and I have somewhat of a hard to talk to old school , and strict mom so how do I suppose to tell her ?