Can lupus cause testical pain?

Absolutely. As an: auto(self)immune(complex internal system which best protects from cancer, viruses, fungi & bacteria), any portion of the body can be targeted resulting in what ever consequences. Commonly, the arterial/capillary system is involved in the self-attacks. Since all the cells of our bodies are dependant on blood supply, they can all be damaged/die even if not attacked as a direct target of the disease.