I'm a guitar teacher and President of the Piedmont Classic Guitar Society. I've worked with Aaron Shearer for many years and helped him with his Mel Bay "Learning the Classic Guitar" books (I'm mentioned as an editor).

If something hurts- stop doing it and figure out what's causing it. You say there's a "stiffness in the little finger of my left hand and the left elbow seems to be stiffening up at times."

You are probably playing a piece where the stretches are difficult and repeating the stretches. Stop playing the piece. Start doing warm-up stretches (See; Aaron Shearer "Learning the Classic Guitar" Mel Bay Vol.2), if there's any sharp pain wait until your hand doesn't feel pain, if the pain persists see a doctor specializing in RSI treatments.

You need to get better conditioning for your hand(s) and keep your left hand as relaxed as possible. A good teacher might help but it's hard to know what a good teacher is.

-Richie