This is an excellent question, because it can sometimes be difficult to tell the difference between a callus and a wart. A callus, as you know, is a thickened area of skin that develops as a protective mechanism to keep the skin safe when it is subject to chafing or friction. A wart, on the other hand, is a viral infection in the skin that leads to proliferation and thickening of the skin cells.
A callus tends to be larger and less well demarcated than a wart, whereas a wart tends to be more circular and may have 'bumps' or depressions inside of it. Also, since warts
are contagious, they tend to spread and there may be several of them located close together. Based on the description you are giving, I think that this is more likely to be a wart, but you need to see a personal physician - either your primary care doctor
or a dermatologist
- in order to confirm this suspicion.
If you do end up having a wart, your doctor will be able to discuss the various treatment options that are available to you to help remove it, so get in to see your doctor at your earliest convenience.