Over here in Canada, and I would think it's also the same in the United States, putting your middle finger up to someone is classed as a rude gesture. It's also called flipping the bird and basically means go away using bad language.
Now why am I talking about this, you wonder? So back in late April, early May I dropped a rock on my finger and it resulted in a blood blister under the nail. One grandson is fascinated with my finger for some strange reason?
Anyhow, when showing people my finger I usually show it like the photo below.
Can't say I thought much about it, until son mentioned that did I realize that when I do that I am giving people the finger..........can't say I did..........oops!!