I never have any fingernails since my hands are so wrecked up from gardening but I have used a credit card for scraping the stingers out of wasp or bee stings.
About switching out the eyedrops bottle for an ammonia container..... PLEASE put a new label on it lest some unknowing person picks it up and uses it for eyedrops. In high school chemistry class we were taught never to reuse containers for poisonous or dangerous chemicals without labeling clearly.