Learninganew, there are some variations on the C and G open chords which use the pinky. When I started learning to play, I was listening predominantly to David Gilmour's style, and on some songs, such as Wish You Were Here, you can hear him using four fingers instead of three to chord it. The ring finger is fretting on the B string on the third fret, and the pinky is fretting on the adjacent E, also on the third fret. When moving to a D chord, the pinky comes up, and the index finger forms a barre on the bottom 3 strings at the second fret. The chord shape "pivots" around that ring finger, making for a fast, smooth transition.
The C chord can also be played with four fingers. Instead of putting the ring finger down on the A string at the third fret, put it on the E string at the third fret and put the pinky where the ring finger usually goes. This doubles the G note in the chord. The Hal Leonard chord finder book shows the C chord this way.
I came upon this forum while looking into my own pinky pain. snow4dayz doesn't mention where specifically the pinky finger hurts. My problem is in the last part of the digit, in the fleshy pad between the joint and the tip. It's happening, evidently, because I have trouble bringing the pinky down properly at high tempo. I'm working on it, but for the time being it seems as though I'm doomed to bring the edge of the finger into contact with the string rather than the tip. The result is something like a crush or blunt-trauma injury to the finger.
I'm hoping I can find tips on how to use correct form with that finger, but as I push the metronome faster, it gets harder to do.