Sounds benign. If the bump has been there for 10 years, has not grown, and is not causing pain it is almost certainly benign. I can't tell what it is from the description, but it could be a plantar fibroma, which is a benign tumor arising from the plantar fascia; it could also be some type of cyst. I do usually recommend having a doctor take a look at it to make sure it is nothing serious.
Appearance? Many interesting things can appear on the sole of your feet. Callouses, warts, ganglion cysts, calcification, moles. Best to have it checked out at your next check up if it's always been the same for ten years. If it changes, then have it looked right away.