Can a lung nodule be caused by sinusitis?

No: Sinusitis is not typically related to lung nodules.

Yes: Usually not malignant, there are entities like wegener's granulomatosis, churg-strauss disease etc that can give you lung nodules and sinus problems. These two diseases are autoimmune but various infections can also give you a similar presentation, most notably fungal. So it is not the usual sinusitis or the usual lung nodule but yes, they can be related.

No: Infections can cause lung nodules, but it would not be related to a sinus infection. Cancer of the sinuses could rarely metastasize to the lungs causing a lung nodule. I recommend following your doctor's recommendations regarding a lung nodule.