If you mean that mottling in the sky, those are JPG artifacts... shoot in DNG, and you will not see that.
Also looking at your JPG, I would suggest that if you want a true B&W version, it would be best to convert whatever original file you are editing, into a true grayscale image... this will eliminate any residual color banding.
IMHO, a bit heavy handed for my taste... but artistic interpretation is so individual... I have my doubts of whether Michelangelo would have appreciated Picasso...
I agree with EEV that the effect was a little strong. A little more subtlety would have focused attention to the sunrise, without wondering why the edges were so fuzzy.
First and foremost, is the photo pleasing to you, and does it convey the message/moment you were capturing in your opinion?