It's A...Whatchamacallit

This a.m., my 6 1/2 y.o. son complained of an itchy foot -- inside his Crocs. We pulled off his shoes and socks, indeed saw a red foot and no doubt a bug bite, put a cold compress on it and forgot about it.

Later in the day, he was resting beside me, barefoot. I looked at his foot again, saw the raised skin and said, "Oh. So do you think it's a mosquito bite?"

"No."

"Do you think it's a rash?"

"No."

"Do you think it's a blister?"

"No."

"No?"

"No. It's a...whatchamacallit? It's a...BOO-BOO!"