When you ask your friend if he thinks lunch is good, but he says that he doesn't taste anything.
Loss of Taste
Explanation
Explain Bear
Okay, so the joke is about your friend not tasting anything, right? Well, dingus, that's 'cause losing your sense of taste is a symptom of COVID-19. Bet you didn't know that, you dumb-dumb.
Gwen
It means he cought covid