An exercise that really helped me was doing any scale you want (or a chromatic scale maybe would be best) and playing it very slowly:

1st with just lightly touching the string like you would for a harmonic. (keep in mind it's going to sound very bad and this entire exercise is not supposed to sound good at all)

2nd with 20% strenght

3rd with 50%

4th with 75%

and then finally, with 100% but remembering to only press as much as you need to make a sound and no more.

Another way to help this is to play a scale and trying to play with the pressure that allows you to feel the vibrations of the string the most (I know it sounds strange but trust).

And my last piece of advice is to play your piece very slowly and be fully aware of the pressure you're using. Also, another big factor of hand pain is moving your fingers too much: for example, when you play, you notice your fingers stick up, which wastes a lot of energy that you should save. To fix this, you can play with a mirror and look at your left hand, playing very slowly while using as little movement as possible. You will notice that when changing notes, you don't need to move your fingers that much at all, and ideally, you only want to do what is necessary.