Anyone have any opinions?

My son woke up multiple times last night and he had started getting a fever when we noticed a bug bite on his arm. But it was small I circled it in case it got bigger and then he went to sleep but this morning he woke up with a tiny one on his armpit and this huge thing on his leg. What should I do? Should I do anything? He’s not bothered by it it seems but he’s never had bug bites ever. I checked last night to see if there was a spider in his bed or something and nothing was there. I just checked again now and still nothing.