Nice idea for selective desat but you need more contrast on the B&W section and less contrast on the purple. Also I think I would have left out the part your holding, leaving only purple in color.
This has great potential but the purple spots on the bottle & the applicator do not match the fingernail polish color. I assume that happened during processing. Good idea though..
perhaps giving the nail polish bottle a bit more room and creating some interesting lines and shapes all pointing to the bottle in the upper 1/3 on the right may have made this more interesting. moving the nail polish brush down to keep it in frame would have helped too