Atrophic scar on forehead following fall on toddler. What can be done to further improve this? (Photo)

6 months ago my son fell against a hard edge. He was fine but was left with this soft tissue indentation that’s only really noticeable when he raises his eyebrows. Resting face, it’s not noticeable except a bit of redness and a very slight skin indentation. What explains the effect of it only being visible when his eyebrows are raised? it’s been 6 months…what are my options going forward to further improving this?