arg. This is a complex topic. Generally, I found that with foot issues, you put the thick edged side of the to the side where the pain is. BUT FIRST make sure that your seat is the right height and that you don't have any Q factor issues.
For me, for example, I had a recurring pain on the outside of my left foot. Had a lot of money into shoes and insoles after fiddling with the seat to get it right. Then discovered that I'm not symmetric and due to a knee injury years ago, I have a wider Q factor on the left than on the right. Getting a longer pedal for my speed plays on the right, made my dogs happy campers but I still needed a 2mm wedge on the left foot with the wedge to the outside.
J.