My noise gets a lot less when warmed up but sounds like a tractor till then.
As said use of 4wd(tractor!!) pistons cures it mostly, but due to the inherant design there will always be a little bit when cold, but a lot more so on 2wd, the gudgeon was moved on 4wd to counter this.
Piston slap causes no harmful effects, and is just a characteristic rather than a fault.
Personally unless it is drinking oil(like mine!!) I would not do anything.
tabetha