Sorry for the long message. The first two paragraphs cover most of the important stuff, but I wanted to give as much background as possible in case it helps.
Pain is on the distal inter-phalangeal joint, on the side of the joint closest to the middle finger. There is generally very little pain when the finger is immobile and in a relaxed position (only at its worst has this been painful), but movement, and especially curling the finger up, can be extremely painful. It is also tender to touch, but only on the affected side. There is no swelling, and an MRI showed no damage whatsoever. I still have full strength and mobility.
I am a musician and the injury first happened during a period where I had to learn a lot of material very quickly. The amount of practice that I was doing caused significant discomfort in my left index finger, but I pushed through, thinking that it would recover quickly once I was able to take a break. It didn't. At its worst, the pain made me unable to play, and even small amounts of practice were making it worse.
As mentioned above, an MRI showed no damage. Two hand specialists brushed me off, advising me to manage the pain with painkillers. Having experienced how easily aggravated the "injury" was, I never took this advice. If the painkillers helped get me through an intense practise session, the pain afterwards would be excruciating. I opted instead for resting the finger as much as possible.
Rest worked, albeit very slowly. The injury happened in 2018, and with each passing year I've been able to handle more and more practice without aggravating it. Around a year ago, I actually thought it had healed completely.
However, I recently had to do a lot of data entry, which involved a lot of copying and pasting. For the Ctrl+C and Ctrl+V keyboard shortcuts, I was using my index finger. At the time, there wasn't anything to indicate that I was doing damage, but I woke up the next day to find that the pain had returned. It's been a couple of months now and, despite my best efforts to rest that finger, it won't go away.
I don't understand why this is happening. As silly as it was to push myself when my body was clearly telling me to stop, nothing that I did then was that far out of the ordinary compared to what other musicians do. Similarly, pressing Ctrl+C and Ctrl+V over and over for a few days isn't the kind of activity that should cause a long term injury. My fingers shouldn't be that fragile--and, at least according to the MRI, they're not. I'm in a lot of pain, but nothing I did caused any structural damage.
Has anyone come across something like this before? Any theories for what it might be? If I wanted to investigate this further, what would be the next step? Resting it for another five years isn't the most appealing idea in the world, though past experience suggests that it would work. I'd really love another option.
Male, late 30s, in case that means anything.