Forehead bone void after brow bossing reduction? (Photos)

You're right, a bone paste or other treatment could fix this possibly.  Another option is to slide in, endoscopically, a small implant that could fix the area.I'd suggest getting a CT scan of your forehead and then sending it to an experienced surgeon.

There are a few options that can address this issue. It can be injected or an implant (various materials) can be placed there. Imaging will be helpful in determining the size of the defect and helpful for planning. Best wishes.

You have a scar and deformity from brow bone reduction. I would go back to your surgeon who should make this 'right' as you suggested to fill it in with bone cement