Can a dinged up prop affect a bass boat's performance.  I hit a sandbar a while back and the prop has some rough spotts and a few tiny chunks off it.  I didn't get a GPS until a couple of months ago, so i don't know if the boat was running this slow before i hit the sandbar or not.  

Yes it will effect your motor performance.  The smoother the prop is the easier it cuts through the water and the faster you go.

Dings,Rough spots and chunks create cavitation points on a prop.  Your prop quickly loses efficiency when that happens.  Go get that thing cleaned up.