It is swollen not swallowed ; by the way any other signs or symptoms or any past medical history ??
If there is redness and heat as well, maybe DVT. Angiography might be needed to rule out. And a blood test can give clues if it is filariasis..
Using the physical sign of unilateral foot swelling it means it's a local problem in the left foot such as cellulites/gout/ lymphatic obstruction/venous obstruction/foot fracture. More history would be helpful π
Depending on clinical complaints you also wonder about DVT