Hey Jonny, welcome to the forum.
Well your background in self-defense and boxing served you well
and even if you developed a problem with your index finger.
I'm certain you would do this all over again, if you encountered a similar situation.
Is there a message, perhaps, in this situation, trying to tell you something?
A shift in your life perhaps is necessary, not just the way you punch the bag, might be the bigger meaning.
Some excess scar tissue built-up and a bit of arthritis, that will do it.
If there's some nerve entrapment taking place,as you attempt to bend your index finger, this would explain the excessive pain.
If this is very important to you, take your time and save the 5K and get it done properly.
I had a couple injuries, one while skiing-broke my pinky- and another one
while sparring and hurt my back badly, so I had to quit martial arts.
I'm OK now, but I have to be careful HOW I do certain things, so extreme sports are definitely out,lol!
I appreciate the insight, and I would imagine that you're right. A shift in the way I do things may be in order, perhaps rehab isn't so much the issue. Maybe its just that I was injured and now the function is permanently changed. I'll stay out of the ring and shady parts of town.
Sorry to hear about your injuries.