What Causes Swelling Of Upper Ear In A Child?

my son will be 3 in August and he is a normally healthy child. He was fine all day until about 5 pm when we left a play date and went to the grocery store. Getting out of the car i noticed his upper cartilage on his right ear is all red and swollen. It is so badly engorged that it sticks out twice as far as the other ear. He says it doesn t hurt r itch but only being almost 3 I dont think he knows what itchy means cause he is continually rubbing it. I don t see any spots that look like a bug sting but should i take him somewhere to be looked at?