I got it now after some thinking, you probably mean: Nail in your
coffin
Here's my honest opinion: the sentences feel to me like a little random, and also cliché.
Secondly, like Lady_A already pointed out, words like "sumthink" are not good write in lyrics of this style; you are not rapping, so better is use correct words. (i.e. 'something')
But from a positive side...I get the message, what you are trying to express
