We have a dog that occasionally (three or four times over the past 4 years) develops them on his face. They're there for a few weeks or months, then the faulty follicle goes dormant and the nail falls off.
I've never heard of one too thick to cut with a clipper, though, teh squishy--your dog's nail might be worth a trip for a vet evaluation.
"We are--each of us--dying; it's how we live in the meantime that makes the difference."
"It's not what you gather, but what you scatter that tells what kind of life you have lived!"
"Be kinder than necessary, for everyone you meet is fighting some kind of battle."