Swelling: In general, foot and ankle swelling can cause discomfort, usually a "tight" sensation rather than actual pain.
Discomfort from swelling tends to occur later in the day, rather than in the morning. Swelling of the legs often decreases during the night (unless you work the night shift.) While lying in bed, there is less pressure on the veins. So fluid in the feet and ankles has a chance to move out of those areas. The fluid is reabsorbed back into the circulation.
Mild swelling of both feet without any other symptoms is often related to veins that are not working at their best. We have valves in our leg veins that keep blood moving out of the legs and back to the heart. If the veins are stretched or the valves don't completely close, fluid leaks into the feet and ankles.
Pain: Pain in both feet can be caused by damaged nerves. This condition is called peripheral neuropathy. It is a common complication in people with poorly controlled diabetes. However, pain from peripheral neuropathy is worse at night and walking should not make the pain more severe.
A common cause of foot pain when walking is plantar fasciitis. The pain is often worse first thing in the morning, getting a little better during the day. You can have plantar fasciitis in both feet, but most often it starts in just one foot. Usually swelling is not an issue.
If the swelling and pain are primarily in one foot, your doctor will consider additional diagnoses.
Find out more about this book:Harvard Medical School Foot Care Basics: Preventing and treating common foot conditions