hard mass on bottom of foot

On the left side of my left foot and the right side of my right foot between the heel and toes I have a callous like mass. The right foot does not bother me but my left foot is a mess. I’m a racquetball player and a food server in a restaurant. I can hardly walk sometimes because the mass gets extremely painful. Sometimes it doesn’t bother me at all. And sometimes there is a numbing feeling. Would you have any idea what it might be? I’ve had these callous like masses for quite awhile. They have not changed at all. Any information you can give me would be appreciated.
Thank youSheryl Rogers