I think erections are probably a bit like when you have a spot on your chin:

You are SURE that it stands out a mile (metaphorically speaking!) and that EVERYONE has noticed it, but the reality is they are probably too busy worrying about the things that make THEM self conscious to see. (Unless of course they are blatant crotch watchers, in which case that's what they're looking to see, so I wouldn't worry!)

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