L.D.
I had fallen one time and bruised my foot in the area that you had indicated. It did swell up and was hard and was very, very painful. I couldn't walk on it or put a shoe on for a month. I don't know if what you are discribing is a contusion on the bottom of your huband's foot but I would probably get him to urgent care or the ER to have a checked out just in case. Better safe than sorry.
Hope his foot feels better soon.