Is the influence limited to a single point or do you want to be able to have an unlimited amount of influencers?
If it is limited to a single (or relatively low number) you can simply use a vector parameter to transfer the hit location of your trace to your wall material. You can then mask out an area around this location in a similar way as I described in this thread:
https://forums.unrealengine.com/showthread.php?54733-Is-this-possible
In your case you probably want a slightly more organic animated edge, but the basic concept is the same.