What is this thing on my leg?? A bite? Pics included!

[AFingerofFudge]

I discovered this tiny red mark yesterday evening on my thigh, slightly itchy but nothing else. No sign of a tick or any other weird creatures. I hadn't been outside, worked in a hospital all day, then supermarket and then home.
First picture is how it looked this morning, definitely a bit more painful. This afternoon's picture is added 2nd, it's frickin killing me and has really swelled up. Could it be a mosquito?? Or something else?

It looks like a horsefly bite. They are utter bastards, worse by far than a mosquito bite.

thanks @Velicirapitor - I can't imagine how I could have got it!

Anyone else have any thoughts please??

It's just a normal bite. I've got several at the moment.

@Mistymountain I really attract all sorts of insects and get bitten so frequently but the pain from this bite is really intense into my leg

Does it feel hot to touch? It's really quite swollen. If you have a pharmacy that's still open, it might be worth asking asking the pharmacist to have a look, could just be a bad reaction and some antihistamine and pain relief will sort it, but it might need antibiotics.
Could be any number insects, if you didn't feel it though, I'd be thinking a tick, mozzie or some other bug which uses a special anaesthetic in it saliva so you don't notice the bite. If you did feel something, then a wasp sting or similar they hurt like buggery the next day.

Ice pack, antihistamine (tablet and cream if you have it)