Sons insect bite behind ear

[Yamaya]

Does this look worrying? Son got bite behind his ear yesterday and was blistered. Tonight it's very red with a tail coming off it. Not sure if this is serious or perhaps he's scratched it?

I've heard about infections with a trail mark being serious, but most images online are on people's arms.

He seems fine in himself and no temperature

Another one

Ouch!

Call 111 for some guidance, see what they suggest. Hope it's not too itchy for him

The management advice here might be helpful https://patient.info/skin-conditions/insect-bites-and-stings-leaflet

Thank you. I've put some germolene on it and marked the end of the red tail to see if it spreads before bedtime.
He doesn't appear to be bothered by it at all.
I would ring 111 but it'll probably be 8 hours or something until they ring us back and will be the middle of the night and I'll have to wake him up etc. so reluctant to go down that route tbh.