Looks like a shotgun blast

As many of you know I've been rebuilding my top end. For those who don't know, it's been long and tedious. I noticed something on #8 piston in the very beginning of all this that looks something like a shotgun blast. It's not centered on the piston but rather close to the edge.

Could this have been caused by detonation? The other pistons look normal but before I close everything up, I just wanted to make sure this wasn't going to cause problems?

Well, you can feel them and they're about the size of a small pinhead.

The overall appearance of the piston looks alright.
There are no scratch marks in the cylinder and the rings look good too.