Pain in middle finger bottom knuckle

I have pain in my middle finger bottom knuckle which seems to be aggravated by gaming, and by extended mouse/trackpad usage. I think it's tendinopathy in my finger extensor, but I am not exactly sure about what it is, and not sure what exercises to do to help it recover. Some details:

- It is normally not painful at rest, but starts hurting half an hour to an hour (varies) into activity. It usually cools down quite quickly after activity. The pain is not very severe, but consistently cuts activity short as I am afraid to use my hand through the pain.

- I think this originated roughly a year and a half ago, where I played through pain for maybe around 2 months (during this period, the pain was sometimes constant).

- I think this has something to do with the ring finger, as the pain originally seemed to be somewhere in between the middle and ring knuckles, and doesn't seem to come when I am using only index and middle fingers. Trilling middle and ring fingers may be a cause, though I haven't tested to see if only doing that motion would cause pain.

- For mouse/trackpad use, I think there's probably some habitual tension causing the pain, though I'm not even sure if its the same issue.

- The knuckle seems to be redder than the other hand's one always, not sure if I'm just imagining it due to putting too much focus on it.

- I have had tendon issues in thumbs/wrists/elbows, but have mostly resolved these through doing high rep exercises and managing load.

For what exercises I've tried, I've been doing something where I rest my palm on a table with fingers straightened and off the table, and placing my other hand on the straightened fingers as weight, and holding. I tried using the 5 finger rubber bands but they seemed like they didn't provide much resistance. I've also very recently started doing some rice bucket exercises, with particular focus on exercises that involve opening my hands against the rice.

What could this issue be and are there better exercises I could be doing for it?