Wrap that foot at the arch with vet wrap. And at home, roll it over frozen roll of corn to help.
It could also be your jeans/breeches or socks are tighter on that side too.
How long since you had feet measured for shoes, as our feet change sizes and that could be what is going on here too.
Have someone video you to make sure you are sitting straight, and not out of adjustment yourself, as chiro might be needed for you too. Do you walk correctly or are you off from side to side?
Horses make me a better person.