Chinese netizens love using abbreviations. “nmsl” is just an abbreviation used as an internet slang.
NM$L/nmsl : Never Mind the Scandal and Liber.
In Chinese, you could say 永远不要理会谣言和中伤 （Yǒngyuǎn bùyào lǐhuì yáoyán hé zhòngshāng）。 It means “never pay attention to rumors and slander” or “don’t give a f**k to the rumors.”
You can also understand “nmsl” as Na Mei Shi Le （那没事了， Nà méishìle）， meaning “it’s nothing” or “everything is ok” or “no problem”.
The images should give you more clues.
国粹输出，蚌埠住了
你tnd还真是个人才，笑得我满地找牙hhhhhh
WORD “NMSL” is n+m+s+l,n is chinese “ni”【你的】/your,m is chinese “ma’【妈】/mother,s is chinese “si” 【死】/dead,l is chinese “le” 【了】/mood word;
the all means in English is “Your mother is dead！”.It like the “fuck your mother’ or ‘fuck you’.