Fillers for Sunken Cheek After Injury?

The key factor in your question is that you mentioned a depression in the area that sustained an injury. Rather than just volumimzing and filling the cheek, the goal should be to determine if there is scar tissue that needs to be addressed. Sometimes, a surgical scar revision is necessary and would have long-term results. However, if the injury crushed the soft tissues of the cheek that can make any mode of treatment less satisfactory.
To add filler to this area without evaluating the depression may result in an unattractive "tufted" look wherein the filler surrounds the depression but does nothing to lift the area in question. An experienced injector will address this to tailor the treatment plan to shape the face rather than just filling an area.
This should be looked at by a facial plastic surgeon and all options discussed .
Hope this helps!

You should consult a board-certified dermatologist or facial plastic surgeon experienced with injectable fillers. You should also see favorable photos of simillar cases.
I've attached a link to a photo demonstrating enhancement of both cheeks with Silikon-1000. I have performed correction of cheek indentations with satisfying results.
I hope this helps, and best regards.

Before having 'sunken cheeks" treated with a filler, you should wait at least 6 months after the injury to allow the injury to fully declare itself. After waiting an appropriate amount of time, I would use Sculptra. Sculptra was developed and approved as a treatment for cheek atrophy.