Botox and Dysport do not directly treat scars. They are used to treat the dynamic wrinkles and furrows that result from the movement of the muscles of facial expression. These substances are called neuromodulators, i.e. chemicals that interfere with nerve impulse transmission to muscles. As such, they do not directly impact on the fibrotic collagen or its formation within scar tissue. However, recent evidence suggests that if these chemicals are injected in around a scar, especially a developing scar, they may reduce muscle activity around the scar sufficiently to allow a the scar to heal in a more esthetic fashion.
For this reason, I routinely inject scars located in and around the facial expression muscles with Botox or Dysport as an initial phase of their treatment. Then depending upon the type of scar and precise location, I follow with either the use of fillers, dermaspacing, medical microneedling, mesotherapy, or scarabrasion.
In this case of an indented linear scar across the top of the bridge of the nose, I would likely supplement the Botox injections with one or two dermaspacing treatments spaced at six week intervals to free up the bound down fibrotic scar tissue and then follow with the placement of a superficial filler, such as Restylane L or Juvederm Ultra XC.