What Causes Fluid Filled Lump On The Knuckle Of Index Finger?

Cut my index finger knuckle about 2 months ago and it healed fairly quickly but was tender to bend so I tried lancing it with a clean razor and then a week later with a a clean needle and only got blood. I had some cordran tape left over from a scar that my son had and it has helped the lancing to heal very quickly but has not seemed to affect the knot in under the skin. The "knot" feels "fluid-filled" not hard. Will the Cordan tape help with the scar tissue if that is what it is or should I try lancing again?