I have round bumps on knuckles of all the fingers of my right hand (I'm right handed), the largest on my index finger
and tapering to the smallest on my small finger
. The largest is about 1/4" in diameter and about 1/8" high. They are rough and feel like callouses, but I don't do any kind of work that would cause a callous there. I can file them smooth or put hand cream on them to soften them, but very soon the roughness is back. The largest is rough enough to snag on clothing, etc.