I had never tried this technique before but am amazed at how well it works.
All you need is: a teabag, nail glue and a nail file.
Rip the teabag (cutting with scissors creates a thick edge that is harder to blend) to cover your whole nail. Coat your bare nail with glue and press the teabag onto the wet glue, smoothing out bubbles and taking care not to glue yourself to your nail!
Once that is dry, do another layer of glue over the top and wait for that to dry. File off the edges so you can’t see any teabag. The result should look like the 3rd photo above.
Put on base coat and nail varnish as usual. Et voila! A perfect fix!
You will have to redo this whenever it starts to lift (which depends on how often you take your polish off) until the split grows out enough to trim your nail properly.