I Have Had What I Assume Is A Blood Blister

I have had what I assume is a blood blister on the tip of a finger for several years. Just got out of the bath and it began bleeding, for the first time. Frim a tiny hole, the blood will jet out of my finger when squeezed - not thick or dark, just regular blood. Would not stop bleeding. No pain. Have put a plaster on it which seems to have staunched the flow. What is it?