Insect bite? Infection advice please

[Grouse]

Hi there,
I'm hoping I could get some advice on this.
This came up on Thursday night

Then by Friday morning this

Vet was called an he's been put on bute and antibiotics
Today

The vet is coming out again tomorrow, but do you think they'll cut an Incision in it to drain it or just leave it to reduce?
I can't believe how fast it swoll up I've never seen anything like it before
But any advice greatly appreciated xxxx

 

[Skipadeedooda]

No idea about the reaction/swelling but the bite type hole looks a bit like what I've been left with in the past after removing a tick. Sorry not much use, hope swelling goes down soon and horse is ok.