They asked us all the questions we had already asked ourselves: were you in the woods or at the beach, did you burn your foot, did you fall or hurt it in some way.... all the answers were no. Finally the doctor came in and carefully examined his foot. Long story short he has a type of ganglion cyst on the tendons of his foot. She explained that typically ganglions are on joints or perhaps one tendon but his cyst seemed to go across several of his tendons. With her help we figured out that when N is on the computer he links his foot on the rung of the chair. It is the constant and repeated pressure from this chair rung that has led to this cyst. Crazy huh? I am so relieved. Me being me had the worst case scenario running through my mind. She suggested getting N's feet measured and making sure his shoes are wide enough. She also said he should use a yoga stability ball for a chair at his computer so that he is forced to keep his feet on the floor, with a side benefit of strengthening his core.
So I'm on the hunt for a large yoga ball and thankful that we have a simple solution.