Pure silicone in droplet form can shift and cause granulomatous reactions. I have seen cases where it has literally caused abcesses and eaten through the skin. It is not approved by the FDA and I would definitely not recommend it. There are other safe fillers that can be injected and even one permanent one if the patient desires. In short, stay away from direct silicone injections.
I assume you mean the fold between the nose and the cheek. I do not consider that a safe location. That is where the major blood vessels and some nerves are located. But, remember, that area is rarely in need of filling. Should there be a perceived need because of some depression or groove or irregularity, usually after an accident, then perhaps surgery would be a more appropriate option.