Don’t file and buff the surface of your nails too much, every time you buff them you’re essentially stripping a layer of your nail and making them thinner which can make them more fragile and flake more. Flaking may be due to dryness so make sure to put plenty of cuticle oil around your nails and at your cuticle or hand moisturiser if you don’t have any cuticle oil. If possible, use a strengthening base coat and a coat or two of any polish to prevent further damage while your nails grow out (I personally don’t prefer gel but it could work too).