iirc the state of california is the only place on the planet that officially recognises any cancer risk associated with nitro fuel.
if its in its sealed bottle then there should be no appreciable risk compared to other risks such as smoking, excessive alchohol comsumption, genetic predisposition and so forth.
the real risk with storing nitro indoors is the fire risk, although that said i've been keeping nitro fuel in my room for years and i havent been burned alive or got cancer yet, despite excessive smoking and drinking.