Try non-gel toothpaste if you don't have any hairspray on hand. If it doesn't produce the same results, try the hairspray.
You just paid a mint to get your nails professionally manicured and somehow ended up with a nasty ink mark across one of them. Since you can't recreate that manicured look at home, remove the ink stains in just a few seconds so your manicure will be looking great again. You don't have to have a ruined manicure even if the ink stain is large and you probably have some hairspray on hand so it won't cost a thing to fix it.
Squirt some hairspray on to a clean, soft cloth.
Rub the hairspray on to the ink stain on your fingernails.
Repeat as necessary until the ink stains have been completely removed.