Painful, Sore, Hot, Itchy Spots On Edges Of Both Feet. Possible Cause?

I have sore spots that are very painful that come up mostly on the bottom edges of my feet...they feel like a soft knot and get hot and itch. They come for about 2-3 days at a time and are not always in the same spot. I actually got one on my big toe last week and another one actually on the ball of my heel this week, but most of them are along the bottom sides of my feet. This has been ongoing for about a year. I can got as long as a month and have none and then all of a sudden i get one and as it goes away i'm getting another, but it is very random as to when they occur. Also I do get them on both feet. Any idea as to what this is or what may cause it. I am on my feet alot at work.