This isn't really supposed to be an option in iOS 7, yet apparently, there's a way to do it anyway. It turns out that nesting a folder inside another folder is indeed possible using this clever method demonstrated in the video below. You'll just need to be patient and fast in order to pull it off.
Basically, what you first need is to make a folder that you want to have placed in another. Then stack two apps together – this will create a new folder, which you drag that other folder into as soon as the new folder pops up. The trick might not work the first time you try it, but it should eventually. Go give it a try!
Thanks for the tip!
source: videosdebarraquito (YouTube)