Brief Answer:
it needs medical assessment

Detailed Answer:
Hello,

a swelling on the foot needs clinical examination to reveal clues to its cause. Potential causes may include:
- bruising because of warfarin. Even minor injuries may cause it. The patient may not remember the injury sometimes. Discoloration is expected because of hematoma formation.
- muscle or tendon injury. Patients usually remember sprains or strains but they may have no memory of it.
- infection. Usually accompanied by fever, redness, warmth and pain.
- vein insufficiency or thrombosis. Clues to vein problems may include engorged veins of the legs.
- heart failure. Pitting edema is common.

Feeling pain usually excludes heart failure and chronic vein insufficiency but I can't exclude any of the rest. Clinical examination is needed and perhaps radiological tests.

Ice can be very helpful for injuries (sprains, strains) for the first 3 days but it won't affect the outcome after that. Try foot elevation and avoid using it too much (avoid moves that cause pain or discomfort). If the affected area is warmer than the surrounding skin and particularly if you've got fever, immediate medical assessment would be required.

I hope you find my comments helpful!
You can contact me again, if you'd like any clarification or further information.

Kind Regards!

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