A lone nanner is no big deal. It's blurry, but if it is one, it's clearly half-buried by growth so it's been there a long while at this point.
Nanners stand out. They are banana-shaped and a bright yellow when mature. pull it out.
Lone nanners dont have a full compliment of anatomy. It produces a small amount of pollen, if at all, and it may or may not be viable polen. You might get a few seeds but it probably hasn't ruined the plant with a ton of pollination.
Definitely don't change your harvest target over a lone nanner or even a few nanners in a tent. They happen more often than you realize. As long as they don't pop all over en masse, you are fine.