The discoloration you see is the Juvéderm injected superficially in the upper dermis or just below the epidermis. If your physician was trying to correct a crease in the skin of the NLF then s/he was trying to place the filler more superficially. If you do not have a crease in your NLF, then this occurred by accident. But it did not migrate there.
The coloration you see is called the Tyndall effect – it is light scattering caused by particles in a colloid, suspension, or emulsion. In the case of hyaluronic acid gel fillers, the light penetrates the skin and is scattered by the gel, producing a bluish-gray coloration. This can happen in any location where the filler is placed superficially in the skin.
This may improve a small amount with time, but it is unlikely to go away. I would allow a few weeks for swelling to resolve and the filler to ‘settle in’. At that point, if the Juvéderm is still visible, which it likely will be, see your physician. This is an easy problem to correct, and a small amount of hyaluronidase can be injected to breakdown the product in the area of concern.
Best wishes, Ken Dembny