I am a nurse and I have seen tons of these and this resembles a wart and a physician should verify this.
Hello, this looks a lot like a planters wart. They grow from the inside out and look very similar to this. Typically they are frozen off at a doctors office. I would make an appointment to verify. They can be painful, and I have had many successfully removed.
Given that it has black around it, and personally, I have never seen a wart with black encircling it, I'd get him to a physician. Why take the chance and let it go, assuming it's a wart, when it could be something else?
It looks like a wart.........that's my guess.
No physician's appointment yet?