Sudden swollen vein in finger! What could it be?

[Twoweekcruise]

All of a sudden my right index finger felt sore (on the fleshy underside near palm). When I looked there is a blueish slight, painful swollen area like a bulging vein. It's quite sore and feels tight when I move my finger.
I haven't knocked or banged it and there are no rings on that finger. It just all of a sudden came up!
What could it be? Can you get blood clots in your finger?

A chilblain?

Spontaneously bursting blood vessel. I get them in my hands sometimes and have also had in my feet. Nothing prompts them they come out of nowhere, suddenly swell up (as the blood comes out and gets trapped under your skin) then leave you with a big bruise. Usually less painful once it's actually burst but ever so weird.

volar retinacular cyst

odd sock could be a chilblain as I get really cold hands.
Petunia sounds very much like it. It now looks like a veiny bruise like mark.
Will off to Google that.

It sounds like Achenbach’s Syndrome. I have had this a few times a year for as long as I can remember. Very painful but mine resolve in a day or two. www.sciencedirect.com/science/article/pii/S153331670500083X