H.W.
My son was stung when he was about 2. He still gets a little wiggy around bees. I just remind him "the bees are working and you, my dear, aren't a flower. They aren't interested in you." and let it go.
My suggestion would be not to force it over the next few days. Honestly, if my son were wigged out about it, I'd leave him in the tent with some books and go about my business. "You are choosing to stay in the tent." and let it go. This is likely more about something unpredictable happening and wanting to control his environment. You can let him make his choice and come to the inescapable truth: you can't control nature! Don't let his reaction control your actions-- go and have fun. Let *him* figure out on his own that hiding away is boring.