Urrgghh, don't like the sounds of that much Flutterby.
I have a problem big toe too, well it isn't a prob, it's just half numb. Exactly half of it. Happened about 15 months after I dropped the grill pan as I was drying up two and a half years ago - July 2010, was holding it vertical with the handle uppermost at the time and it landed long edge first on the nail bed. Rendered me speechless for about 15 minutes, so you'll be able to judge how painful that must have been.
Anyway hurt like hell for about a week and subsequently only if I prodded it, for a while, then stopped hurting. Never had a black nail or anything, although there is a ridge across the whole width of the nail that hasn't grown out yet.
When it went half dead (the RHS of my left foot) and only slightly down the side of the toe I enquired about it and they all say - Oh it's diabetic neuropathy. Can't do anything. It's only half numb though - can't feel it when they tickle me toes with the gadget, but if I touch it with a finger I can, or a blunt pencil or anything really, just can't discern what it is that's touching - so if the thing touching it was pointed like the end of a skewer for instance, I wouldn't know that and might think it was something blunt eg the rubber end of a pencil with a rubber. But I should know if it was touched at least and inspect it.
I don't personally know anyone with neuropathy in their tootsies, so does it sound like neuropathy? To be that isolated, that 'woolly' and not cause any pain or discomfort?
Completely pink and healthy looking, just as I say, cut 9 toe nails once a fortnight in summer, 3 weekly in winter, and that one - months apart between trims.