Bump on my wrist bone? Any ideas of what this is?

Just the other day, I noticed this bump on my wrist bone. its very small. its really strange because you can kind of move it around. I've never had any wrist injuries or anything. Also you can kind of see the bump sticking out. Its not squishy, its hard. This might be a weird way to describe it, but when you push it hard, its slides out from under your finger. No, it doenst hurt at all. I probably would never of noticed it. Help?