I don't see what you are pointing to.

How did sandpaper fill it?

I think you are mistaken on how sand paper works.

At any rate, the picture shows the crack to be pretty insignificant and doesn't appear to be in your track anyway. By the very nature of their intended use, bowling balls get scratched and cut.

Bowling balls are going to get banged up. Even if that scratch is in the track, it won't affect anything. Most balls have engraved logos and such that often fall into a player's track - and that scratch looks harmless compared to them. That, or I'm not seeing what you are talking about.

You should go get the indentation in your head looked at first.

I say wipe it down with those groovy pants you have on, that just might help.

Is a little light in the wallet as my USBC card expired. It is not on my track but may the indentation affect the my revs ?  My revs are very important to me as my tilt is one of the weaker ones.