We've all had them and wondered, "how the heck can this stupid thing hurt so darn much?" While you probably already know that most paper cuts occur on your finger tips and that they have more nerves than most other areas of your body, you've probably still wondered why a knife cut in the same spot seems to hurt less. Well, Mental Floss can help fill you in:
Well, the blade of even a fairly dull knife tends to be more straight and sharp than the dull and flexible edge of a piece of paper. When a knife cuts your skin, it leaves a relatively clean cut compared to paper, which will flex a little and do more microscopic damage to the skin.
There's more to the story, of course, but you'll have to visit the link to read about all of that.
I remember something about this and papercuts in my book "Neuroanatomy Through Clinical Cases" by Hal Blumenfeld.