Should I be concerned about this mole on the sole of my foot? (Photo)

If you have any concern at all, I recommend having the spot examined by a dermatologist. Routinely, dermatologists perform dermoscopy and serial imaging to assess for worrisome features or changes. A biopsy is often very helpful.

Please consult a dermatologist who can examine your mole and give recommendations for possible treatment.

It is impossible to give proper diagnosis from a photo, but in my opinion, moles that appear on the feet particularly, should be biopsied. I know you said that you don't know whether the site has changed or not, but I would suggest you see someone in person who can look at it again, and suggest that you biopsy it for proper diagnosis if the doctor suggests it.