Translation:Someone's ugliness does not need to be known by everyone.
Aha...okay...do you have another alternative as well ?
I would translate 'someone's flaws' as 'kekurangan seseorang'.
I think 'flaw' is too mild as a translation for 'keburukan'.
How about: 'badness', 'evilness', 'foulness', 'nastiness', 'wickedness', or something similar?
Or does that sound strange in English ?