I've been looking forward to building up calluses on my fretting hand to make it easier and more enjoyable to practice. While examining my fingertips today, I noticed that they tell a story.
Right after noticing that I was fretting too hard with my index finger I noticed that that finger it's the only one that shows major callus build up. At first, I thought that it was due to the simple chords I was learning using just one finger but my ring finger doesn't show the same abuse. This may be partly due to the third fret being easier to push down, but I'm sure that it is mostly from fretting too hard with my index finger.