I started playing guitar in December of last year, but a month ago I switched to the bass and I feel way more at home. I'm sure you guys know the feeling. Anyway, I've started to develop a really weird sensation in my fretting index finger that's bordering on pain. On occasion throughout the day, though almost always when I wake up in the morning, that finger will be stiff and sore, and the feeling doesn't go away until I pop the joints in both directions (first away from my palm and then towards). Throughout the day, I can pop that finger by curling it towards my palm almost on command. I play for an hour or two five or six days a week. I use one finger per fret on my MiM P-bass string with regular Slinkies in standard tuning, and I usually play sitting down with the neck angled slightly above parallel with the ground. I shake out my arm and stretch between my fingers before I pick up the instrument, and my first warmup exercise is a 1234 spider walk starting at the 9th fret working my way towards the headstock. Occasionally my thumb gets sore, so I know that I'm pressing too hard, but is that also why my index finger is feeling so strange? What could I be doing technique-wise that is causing this, and how do I fix it?