If you've just started playing and your fingertips are killing you, you might try using lighter-gauge strings: lights are much softer to press down than mediums, and silk-and-steels are even softer still. Coated strings like Kürschner, though more expensive, also do not dig into your fingertips as hard as regular strings do. Another consideration is action: if your strings are higher off the fingerboard than they need to be, some inexpensive setup adjustments might really help. Be sure to pace yourself while you play, too. Short, daily practice sessions are better for building calluses than one marathon a week.