Of course I wish the size 50 that a sales-droid talked me into buying *were* leather because then they might have stretched enough that I could wear them without my toenails falling off.
All kidding aside, you may have much worse problems than "nails falling off" if you wear too-short shoes.
Who's kidding about "nails falling off?" I haven't had it from cycling, but that's a prominent failure mode for me and ill-fitted shoes.