If I were doing that build, I would just sand out that ding in the horn. I would also have a go at sanding those cracks in the end grain as well. The don't look that deep and it would be good to at least make sure that all the glue (or filler???) is gone from there.

With the horn, I know it will alter the traditional tele shape a bit, but I personally prefer making the edges & horns more rounded than standard strats & teles anyway, but that's just me...