I don't think the "social order" would change much.
Maybe a few men who currently have - or feel they have - a relatively small penis could focus on other issues instead, like economics, science, engineering, agriculture. Things that matter. It might have overall benefits in that way?
But I don't believe that much of our social interaction depends on penises. The risk that it might is probably why loincloths and then clothing were invented. I'm not sure if you look at centuries / places where penises and/or codpieces were widely displayed, you'd see any specific kinds of social difference?
Compare it with intelligence, or physical prowess - muscle etc. Those are highly variable, and it all works ok. We develop systems of measurement, and training. We try to help each other. We celebrate success and create incentives. There are things that are appropriate if you are intelligent - becoming a professor, doing crossword puzzles etc- but nobody minds if you don't do those things. And there are things that are appropriate if you have physical skills - becoming a football player or lumberjack. But again it's acceptable not to live your life in that way. There are alternatives.
I think the issue with penis size is that you can't do much about it. There are surgical options, but even that hasn't made huge difference to society. Maybe because of risk, and/or cost, but more likely because it's not a priority for most people.
So, if you do look back at those times or places where penises were displayed more - or loincloth bulges, codpieces etc. - other than being a bit more about physical interaction ( hunting, fighting etcetera ) and a bit less about intellectual or spiritual things, it's hard to recognise complete difference. Or to know which is cause and which is effect...
Personally I'm happier with the more philosophical side of life. If we all wore togas or kilts and so on, I think society might be better. I wear a lot of Lycra/spandex at the gym and so on, because it keeps my body cooler for a workout, but other than that I'd be perfectly happy if nobody had any knowledge of my genitals. So them being a different size or shape would be of almost no relevance, to anything ...