Did he give you water pills to relieve the fluids in your body? Be careful not to eat too much salt because your body retains the liquid and make sure you elevate your foot. Make sure your lymphatic systems are working correctly and a support stocking can help your foot too. I use it for my husband whose foot swells from time to time. It could be poor circulation too. Just a suggestion.
There are so many questions that it is impossible to even begin to answer your question. We would need to know your age,what kinds of activities you do, shoes you wear, family history of these sorts of things,what you eat/drink, your weight, does it come and go or when does it swell, what medications are you on, do you drink,smoke, is there pain, ...the questions are endless. If this condition doesn't go away then seek a second opinion. good luck