Sounds like just the way the nail is growing - is it sort of thick and slightly wedge-shaped where a 'normal' nail would be sort of spade shaped?
If so, join the club. I file this type of nail down on its face so it looks like the others, seal it with clear varnish and then polish it. I don't think it's an ailment or needs curing, it's just how it is.
Thx for the info Mosaic. Shall persevere with the manicuring tho I sometimes wonder if there is some kind of vitamin deficiency but I'm not losing sleep over it!