Is there any way to reverse a facial scar happened by accident?

No: There is no way to “reverse” or erase a facial scar. However, it may be possible to ( depending on the exact nature of the scar) to improve its appearance. Sometimes the use of products (silicone based for example) superficially, injections (steroid), “resurfacing techniques” (laser for example), and/or scar revision surgery may be helpful. Best wishes.

Erasing scars: You cannot erase a scar but you can do procedures that help camouflage it so that is is barely noticeable.