How can I treat this scar on mandible bone? (Photo)

Subcision, a simple, relatively inexpensive minimally invasive procedure I have been routinely performing since 1995 has a seversl decades' long proven track record for both safety and efficacy for elevating and smoothing all kinds of indented (atrophic) scars (from all causes, including chickenpox). For achieving optimal improvement there is a window of opportunity for treatment between the end of week four following scar appearance (a time when the wound is strong enough to withstand treatment) and week twelve (when the scar is considered "mature" and beyond which optimal improvement becomes unlikely). So, you would be wise to seek consultation with a board certified cosmetic dermatologist asap during this critical timeframe, and best of luck.