I am living the real-life experience of what happens when you don't wear shoes and there's a needle somewhere in your house. At some point in the recent-ish past, I apparently stepped on a needle and got it into my right foot. Then on Thanksgiving day, I managed - with the talent only I have - to move that needle into my right arch.
Last Thursday I had to have that needle surgically removed. I am now a bit restricted in my movement and banned from stairs until at least Friday.
Moral of the story, little ones, is ALWAYS WEAR SHOES!!!!