What is the risk of injecting filler in the nasojugal groove area?

This area is often considered an advanced area for injectors so often for less experienced injectors they will avoid this.  There is a certain level of bone that sits beneath this area and as long as you stay within the boundaries then you are generally safe.  However, if you inject above this bone then you can cause serious harm to eye.  This is extremely rare and would require multiple errors to occur.  Most mistakes though are done by injectors who inject too superficially and this results in lumpiness which looks quite bad.  Also, in this area, it is more common to bruise so poor technique can potentially cause bruising that lasts weeks.  If you are interested in this area, you must seek out highly experienced injector who has done countless times to minimize these risks and get the best possible result.

All filler injections carry the same risk, regardless of area injected. Nose filler, jawline filler, and lip filler are the highest risk areas. knowledge of vascular anatomy(both location and depth) is something a skilled injector should have. Further safety can be achieved by using canulas, which do not have a sharp tip, making it extremely difficult to pierce a vessel. Particulate fillers like sculptra and radiesse carry a higher risk than gel fillers. Nasojugal injections can be safely done with hyaluronic fillers injected with a canula. 

This is a more advanced injection requiring more advanced anatomic and injection knowledge. That being said, it can be safely done in the appropriate patient. I prefer to use Restylane for this indication and inject it using a microcannula to minimize bruising, swelling and risk of vascular injury.