There are many different causes of foot swelling, some which are very serious and require medical attention. I would recommend that you discuss this with your primary care doctor
and not just your surgeon
(although discussing it with them is also important).
After a surgery
, there is significant inflammation that occurs. This inflammation, caused by the procedure itself, causes damage to the area including the small blood vessels that carry blood to and from the foot. With damaged vessels, it is possible that the fluid has a harder time returning to the heart as it leaks out of the blood vessels. As such, it is possible for occasional swelling, likely after standing for a long day.
There are other causes of of swelling that require attention. One is blood clot (deep vein thrombus) in the blood vessel of the leg. This is more common after surgery. If the clot breaks off and goes to the lungs, this can be fatal. While unlikely, talk to your doctor.
Other causes of feet swelling are more common if both feet are involved. These include problems with the heart, problems with the liver, and problems with the kidney.
Talk to your doctor. There are some causes that should be ruled out.