Really nothing you can do except let time heal it, the tree will eventually cover the damage, will take awhile, but the tree will do the work. If you really wanted to get rid of it or blend it in to a design, you could chop it right above the damage and do a smaller tree.
Hard to tell from the pics but it looks like an older wound that is starting to heal and curl over. As @Housguy said - nothing but time will take care of it but it shouldn't be detrimental to the trees health.