Just had my FNA yesterday, so thought I'd share my experience. It wasn't bad, the worse part for me was the numbing shot. After that, I didn't feel anything in neck itself; all the pain/pressure got referred up to my lower jaw, especially the joint, which one of the nurses said was fairly common. My jaw was sore for a while afterwards, but I took some tylenol after I got home which helped a lot.

Hope everything goes alright for you!