[Question] What is this on my finger?

The flesh between the first and second joints of my little finger has hardened and started to bulge out.

At first, something resembling a blister formed.

Since there was no pain, I just left it alone, and as time passed, it hardened and gradually grew larger.

It feels a bit like a bump when I touch it.

It's hard to see in the photo, but it's really annoying when my ring finger and little finger bump into each other.

Since I'm paying attention to it, I keep touching it, and it's becoming uncomfortable, feeling like a very hard lump.