What a funny story, Elf. Some of my boys went through a nail polish phase too.
I remember once when we were on a trip and through a variety of mishaps, it got late and my then 3 year old son was really hungry and trying to contain himself. We went to a McDonald's I think and when we opened up his little burger, they has mistakenly put pickles and onions and catsup on it. It was almost too much for my little guy because he was starving. I quickly told him not to worry, I can get it off, it will be all gone as I was trying desperately to scrape off the offending condiments from his little burger.
A lady next to us piped up and said I should teach him to be grateful for food when he got it and to eat what was put in front of him. My little guy was shocked and stopped whining and turned around to look at her. Then he whispered really loud in the direction of my ear "I think she needs a tummy tickle" (which was what I would do to him if he was crabby or cranky). I couldn't help it - I laughed and said to him "Do you think so?"
The lady was not amused and made a big production out of moving to another spot but I always thought my boy was right. That's exactly what she needed. The lady who poked fun at your son's fancy nails probably really needed a manicure, too, even if she didn't know it at the time!