a good podiatrist or podiatric surgeon? I ask because it could be [tho mite not be] something in the actual foot structure. An exam and good set of x-rays can eliminate a lot of the worser possibilities and could put your mind at ease. Do keep in mind that that foot has a whole slew of nerves [almost as much as a hand...and that's billions of 'em] and have something rub one the wrong way and well...the rest is history.
Start out simply in the 'doctor world' and work your way up that 'food chain' if needed, when necessary. Hopefully it won't be?
That all said, it doesn't make it hurt less in the meantime.
Let us know how things go! Hope always - j