Red spot out of nowhere

So this large red mark has shown up on my boy this morning. I thought it was a mark from falling asleep on his hand at first but it hasn't gone away in over an hour and it's warm and very slightly risen. The first pic is from Sunday, no redness on his face at all. Second pic is this morning at 7am and then the last three are from an hour after that. I'm not sure what it is, doesn't look like a bite but I don't want to rule that out. He hasn't eaten or came into contact with anything new. I just don't know what it could be and wondered if you might have any ideas? Thank you in advance!