Quite hard to show here but my nails are relatively smooth on top but thick underneath.

Quite hard to show here but my nails are relatively smooth on top but thick underneath. The thick stuff underneath isn't fileable with an electric nail file or any other file. Its almost like thickened/hard skin and not a hard/brittle texture so I am unable to file it. Its quite painful to prod and if I get the file on it, it'll bleed. Any recommendations on getting rid of this?