That is strictly caused by the fretboard shrinking over time. My repair guy Eric's Guitar in Van Nuys, CA says it's important to keep the fretboard 'lubricated' by wiping it with a fretboard conditioner from time to time, especially if you're in a dry environment....I had to take it to a local luthier to have the ends filed smooth. It might have been from my style of play but my finger nails would get caught between the fret wire and neck. Again a good set up will increase your playing enjoyment. Good luck!