Do nematodes have organ-level organisation?
In Fig.1 is shown the body plan of a round worm:


Fig. 1. Nematode. source: University of Illinois

You ask whether there is an organization in terms of organs; an organ is:


  A group of tissues that perform a specific function or group of functions;


A tissue is:


  An aggregate of cells in an organism that have similar structure and function;


As you can see in Fig. 1, there are clearly organs present, including a mouth, pharynx, reproductive organs, among others. They fulfill different tasks and contain various tissues, each dedicated to specific functions. Hence, they fulfill the definitional requirement of being organs.