Ah @crafty! You are the only person I can recall who's had this problem since I had it during my chemo earlier this year.
What chemo are you having? I had TC. First round for a few days my finger and toe nails were tender when you pushed them. Second round a little more painful and for a few days longer. I could see brown semi circles appearing under the nails, half way up. Third round, way more painful, nails started to lift and my hands were sore. It hurt to clap and touch things. I found some white cotton gloves at the chemist to wear to protect my skin when I was driving. Where the pain had lifted before the next round, it didn't this time and the fourth round the pain intensified. I had to use a haptic pen to type on my phone and couldn't fold laundry; the fabric was too rough on my skin! Using a towel was difficult. I wore the gloves to push the supermarket trolley. I was useless at doing pretty much anything with my hands.
Once chemo finished it slowly receded, though one by one all my fingernails lifted after each one got the brown semi-circle. My toes also discoloured, some quite badly and I ended up losing three toenails, including both the big ones. I didn't lose any fingernails, though it was months before I could use them with confidence.
My hands stopped hurting, though I've been left with the slightest lack of feeling in my right fingertips. My oncologist said that it was probably the same in my left hand but as my right is the dominant hand it's more sensitive and noticeable.
I had a series of ridges appear in each fingernail. Eventually I realised that each ridge (there were four) corresponded with each chemo infusion. It was with great joy that I saw the last one grow out a couple of months ago but my nails haven't returned to their former glory. I've always haf really strong, hard nails. Only the pinkie finger on my left hand has recovered. All the others break in a weird way the moment they get beyond the end of the finger. They're soft and flaky and it's really irritating! And a constant reminder of chemo... My last infusion was on 8th March this year.
I hope they get better soon. My big toenails are slowly growing back. The right one has a really big lumpy ridge. A few more months and I should be able to cut it off. Can't wait! K xox