What causes busted blood vessels in the finger. Mine keeps getting worse each time and it is always the same finger and I don't have to really be doing anythig and it will bust. This time it is black all the way down my finger.

Have you been to a doctor to get properly diagnosed? Could be permanently impaired small capillaries.

You need to see a doctor, like... a while ago before it got this bad.

Have you had an accident at some point,maybe caught that finger in a door or something similar?
Perhaps you have done this injury to the same finger on a number of occasions, which has damaged the blood vessels!

Best thing is, go see a Doctor who can have a look and also give you the correct treatment and diagnoses.