There is no such chemical compound or substance as "silver nitro oxide." The fictional compound was part of a 2013 social-media hoax which claimed that scratch card tickets contained the allegedly carcinogenic material.
The silver coating on scratch cards is made from specialized UV inks or latex. There are no credible scientific or medical sources that claim these inks are in any way carcinogenic. The hoax claimed that the "Medical Research Authority of the US" and a "Dr. Brian Berry" had discovered links between silver nitro oxide and cancer. Neither of these entities exist.
Two compounds with similar sounding names - nitrous oxide and nitric oxide - exist, but silver has no association with either one.