Ever get a paper cut? They hurt. You think it's insignificant, but they can be very painful. Not a serious injury by any measure.
Now...ever get a paper cut on the index finger of your fretting hand UNDER THE FINGERNAIL?
OUCH!!!
About a month ago, I was making my bed, and my mattress has these handles on the sides, well I reached down and got one of the rivets, I guess it was, holding the handle to the mattress right between my picking thumb nail, couldn't hold the pick for about a week.