2nd time it has appeared in the last 2 months. Right under the ball of my right foot and in the middle. It is very painful to walk on my right foot
You could have something called Morton's neuroma. Morton's neuroma refers to a thickening of the tissue that pinches the nerves in the toes causing the nerve to become inflammed and painful. Massage is reported to help as well as roomier and better shoes. Basically its a problem of misalignment of the feet. This suggests that stretching exercise that re-balance and realign the structure of the feet could be helpful as well.
The fact that it's red may indicate infection. Obviously, it could also simply be inflammation, but you should get it checked out because foot infections are dangerous: there's less tissue, so it gets into bone easier.
I hope it's nothing too serious.