It may be a case of slight RSI. But we are no doctors (Unless some of us are!).
RSI can be quite serious. A few tips though…
Make sure when you warm up, you start off with warm ups that have no big stretch. Just get your fingers moving is what you’re after. Go for a chromatic scale or run up and down a major scale slowly. Between warm up scales, stretch your fingers lightly. Just before you feel that big pull, stop and hold.
Practicing the same thing repeatedly can be pretty bad and very tiring for the muscles. This might seem contradicting, as we get better by only; Eating, sleeping, practice; repeat. But kind of use the example of going to the gym. You dont get big muscles from using the same weights machine 7 days a week for 3 hours a day…If all you are doing is building biceps, you will cause damage. This kind of works in the same way. If all you are doing is lots of barre chords, then you will over do those muscles.
It’s pretty straight forward advice so you might be aware of these 2 tips, but try to vary your practice.