My husband is a surgical tech and is on his feet all day. He is also overweight. Tuesday he came home complaining that the bottom of his right foot was hurting. The swollen area was from the outer edge to the bottom middle portion and extending from the big toe to his heel. I looked at it last night and it was swollen and kind of grayish blue. The swollen area feels hard when you touch it. I am really concerned. What could it be?