Re: Dings on a SS prop.
Can't see much in the photo.
Yes you can clean it up with a file or grinder. Yes the ding will cost you a bit of performance whether you clean it up or not. How much? Subtract your current top speed from your pre-dinged top speed...that much.
A prop shop can recondition the whole thing and make it like brand new for $150-ish or maybe even less if you find the right place. I just had a few minor dings and 1" of pitch taken out of my 4 blade stainless for about that...
I consider such reconditioning of my stainless prop to be annual or semi-annual maintenance...or most anytime I notice flaws. So if I were you I'd have it fixed. But I'm a perfectionist...you may not be. 'Tis optional.