"alan_m" wrote in message
...
On 16/05/2021 07:39, Brian Gaff (Sofa) wrote:
I would show it to a doctor. It could have a fungal infection underneath
which is perpetuating the split. After all as you surmise, what should
happen is that it will grow out if you are careful to cut it square each
time, but if there is something growing under it that will never happen.
I
had this with a big toe nail and it was not until I got rid of the stuff
underneath that it grew out again. I',me surprised its a finger nail
though
as they are in the air and readily exposable to various chemicals that
fungi
won't like. Inside a shoe its more conducive to nasty things.

I had a finger nail that for around 5 years grew with a vertical ridge
after hitting the base of the nail with a hammer. As the nail reached the
end of the finger the ridge would split at the ridge line. The only way I
could keep it from snagging was the file the nail flat every week. At the
end of this 5 year period the ridge started to disappear and afterwards
the finger nail grew normally flat to the skin.

When I was in my teens, I bashed my foot (I was wearing socks but no shoes!)
on the sharp edge of a concrete doorstep. This broke the nail off at the
nailbed. Bloody painful it was, but it grew back.

However when it grew back the nail was not flat but was arched, both
side-to-side and front-to-back. And it continued to grow like that. What is
interesting is that something caused the nail to come off again some 20
years later: the old nail remained in place but the new nail grew underneath
it, until it pushed the old nail off. And that new nail has also grown
curved.

I imagine the trauma of the injury damaged the nailbed in some way, causing
the nail to grow in a non-standard way. It's not a problem, except that it
is much thicker and hornier than all the others, so it is more difficult to
cut - and it needs to be kept fairly short otherwise the tip of the nail
starts to grow into the toe.