Doctor here, please do not fear me.
Isolated swelling of one leg is a sign of deep vein thrombosis which can lead to pulmonary embolism which are kinda serious. You should have that checked out right now. Heart failure as another commentor said is unlikely since it's only single sided. Lasix is also not the treatement of choice for this since single sided fluid buildup is very rare.

Ofc. It could be totally benign, but from across the screen without further information this is hard to judge and it could be deadly so better be safe than sorry.

That looks bad fam. Did you hurt it, or is it just swelling? Is it painful?

My wife's ankle sometimes swells if she's been wearing restrictive shoes or her allergies flare up, but its not usually by this much.

I get the doctor thing. I would just go to an urgent care for something like this so they can tell you if its something to worry about or not. Those are usually pretty quick and cheap, but YMMV.

Wishing you best of luck, no matter what!

Free feet in this economy?

Can't figure out how to say this without it sounding weird but thank you for maintaining your toe nails.

So glad you went. Never fuck around with infection, especially like this. I hope it gets better soon!

Between this and your other concern, I’m glad you went to get things looked at. Neither was a good sign of things. Better to see a doctor then end up in a worse situation.

This exact thing happened to me last year after I got a huge cut on my leg after an e bike accident. Turned out to be a skin infection (cellulitis). They prescribed some antibiotics and it got better after a few days. Best of luck, op!

Was the ER able to take care of you? I hope you’re doing OK!

It could be the sign of a weak heart. I'm not saying you're in heat failure, but people in heart failure get fluid build up in their feet/ankles because the heart is having trouble pumping the fluid around. This might be a sign you need to get checked out.

Holy fucking hell!! That looks terrifying! Glad you went to the doc! What do you think the infection was from??? Did you cut your foot somewhere?

I just went to the doc for some weird clusters of blisters scattered across my right leg/foot, some of which had been painful. The urgent care said they looked like bug bites but they were taking forever to go away. My mom is a nurse and she said it looks like shingles. I'm traveling so it's hard to go to a doc a this point. It's been over a week and at least it doesn't feel worse so I think I'm past the point of antivirals doing anything. Annoying this.