This sounds like a weird method but it actually works. I learned it several months ago from Dee and it's my secret to recover cracked nails when I accidentally chip it with intense keyboard typing.
If you have time you could watch the video tutorial for step-by-step instruction. You do need a nail glue for the method above.
In a rush? Follow the steps below:
(No Nail Glue Required)
What you need: a tea bag, a fine medium grain nail file, buffer, a base coat
1. Buff nail to smooth out cracked nail.
2. Cut of a section from the tea bag (enough to cover the broken nail).
3. Apply the basecoat.
4. While still wet, place cut-out tea bag on. (tip: Cover the nail halfway if it’s a crack, and a third of the way if the tip is peeling).
5. Press the tea bag down to make sure the surface is smooth.
6. Finally add on another layer of base coat and you're done!