Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice.
Swollen ankle might be caused by certain medical conditions including (being overweight,
venous insufficiency,
blood clots in the leg, kidney failure,
heart failure,
rheumatoid arthritis).
It can also be caused by some injuries including ankle sprain and arthritis or by taking some medications.
However, if you stand a large part of the day, you can develop a swollen ankle. It's the most common site of swelling because of gravity’s effect on the fluids in the body and in my opinion this is the cause of your ankle swelling.
You ca try to rest, elevate the left leg above yor heart, put some ice in the swollen area and also you can use anti inflammatory drug Ibuprofen.
I after this treatment the swelling gets worse, or you feel any other complaints then you should consult a doctor, for a physical examination.
Hope I have answered your query. Let me know if I can assist you further.