I have a blue lump 5mm in diameter at the base of my index finger on my left hand i have had it for around a year but just lately seems more prominent?

A couple of thoughts: My first thought is that this is a thrombosis/blood clot in a digital (finger) vein. It may initially have been painful but after a year, the pain is gone and the blue lump remains. It could also be a discolored ganglion cyst or even a skin tumor including melanoma. You could send us a picture for further help, but your best option would be to have a Dermatologist examine you/it. Good wishes:)