Thank you for that.
Well from your description, it sounds to me as though you have a problem with a sensory nerve in your cervical spine.
Every part of our body is supplied by nerves coming from the spine. The nerve which supplies the lateral forearm, thumb and index finger is in the neck or cervical spine.
It is quite possible that you have had a mild degeneration of one of the discs in your neck for some years and as time has gone on it has impinged the nerve which supplies your index finger.
The pain you felt today on waking could have been due to your position in bed. An impinged nerve however minute will always be susceptible to inflammation if it gets extra pressure on it which will result in numbness and/or severe throbbing pain.
An MRI would prove or disprove this theory.
The only other thing I can suggest is narrowing of the tiny blood vessels supplying your finger. This would cause throbbing pain as the blood pulsates with each beat of the heart trying to push through the vessel.
It is a bit like a three lane motorway (or freeway depending where you are) suddenly and without warning having two lanes shut. If you can imagine the volume of traffic trying to get through as they attempt to merge from three lanes into one and the stopping and starting as one car lets another in, it will give you a rough idea what goes on in the blood vessel. The only problem with this theory is that I would have expected the tip if the finger to be white or blue, and cold.
I still feel that my first theory is more likely to be the correct one. What makes that fit even more is the relief you are getting from ice.
It would be worth trying to see a neurologist who would be able to help you with this.
I hope this helps a little and I do sincerely XXXXX XXXXX better soon, this sounds extremely painful you poor sweetheart!!
With my very best wishes