Is it on a joint? Is it red, or is it "hard and white" ?

When you press on it does it go into the finger? Or is it stationary? There can be calcium deposits on fingers too. That complicates matters and diagnosis.

Duypuytren's is inherited. It is a collagen defect if I am not mistaken.

There are nodes on terminal joints that form that are osteoarthritis, and are called Heberden's nodes.

I have Heberden's and some knots on tendons between joints. I put my magnesium lotion on them every day, and they go down some, and stop hurting, but do not go away completely.

There are lots of things that happen to fingers..so only a hand doctor would be able to give you a good diagnosis.

Look on Google images, and see if you can find one that looks like yours.