Diagnose needed please

II guess when I say soft, I mean the nail near the end tends to flake/crack right by the line and catches on most everything.  I can trim it down, but eventually as it grows out, it cracks/chips again.

This looks just like my nails did 3 years ago.  It was Lichen planus of the nails and, 3 years on, my nails have all but disappeared.  If it is lichen planus, you need early treatment.  My dermatologist tells me that the treatment (which is not pleasant and involved injections into the nail) is almost always successful.  Unfortunately, in my case, it wasn't but then I was quite late getting a diagnosis.  My GP practice had not seen lichen planus of the nails before and it was only because I already had lichen sclerosis and told them I thought it had crossed over into planus, that they referred me.  I attach a photo of my nails from about 6 months ago - they are much worse now.

Hi DonH, for more information you could search the internet for brittle nail syndrome and onychorrexis.

Kathryn07219 mentioned it could be caused by a skin condition called lichen planus.

Other causes include a fungal nail infection, nail psoriasis, an underactive thyroid or overactive thyroid, reactive arthritis, trauma to the nail, prolonged contact to water and detergents, etc.

Since it only affects a single nail it might have been caused by trauma to the nail and damage to the nail matrix.  

An article in the national library of medicine (I will  send the link in a private message) suggests it might help to apply a special clear laquer containing proteins to strengthen the nail. Maybe you could apply such laquer to the tip of you nails to prevent breakage.