Brief Answer:
Detail below.

Detailed Answer:

Hello,

Pain and swelling in foot may be due to many reasons .
1. Ankle or foot injury
2.Congestive Heart Failure
3.Kidney Failure
4.Being overweight: Excess body mass can decrease blood circulation, causing fluid to build up in the feet, legs, and ankles. Standing or sitting for long periods: When the muscles are inactive, they can't pump body fluids back up toward the heart
5. Osteoarthiritis
6. Liver cirrhosis

These are main cause responsible for pain and swelling in foot .
Kindly give more history and if possible upload photo of foot so that I am able to help you in better way.
Till then you can do hot fomentation,elevate the limb at night and take ibufrofen if pain is there.

I hope this answers your query.
In case you have additional questions or doubts, you can forward them to me, and I shall be glad to help you out.
Wishing you good health.
Regards,
Dr. Praveen Tayal

---

Brief Answer:
Can be due to standing or dietary changes.

Detailed Answer:

Hello,

Only swelling can be due to increased salt intake, standing for long hours, use of laxatives, hypertension, etc. You need to consult a physician for a few investigations in case the swelling persists. Till then do keep a pillow under your legs while resting.

Hope my answer is helpful.
Do accept my answer in case there are no further queries.
Regards

---