Assuming it was a very gentle kiss that ground off the tip and not something that snapped the bits off so that it didn't affect the root area of the prop you should be OK. I'm far more worried about the structural integrity of the prop after stuff like this than the motor to prop efficiency. You should be as well.

You don't give any idea of the diameter difference between before and after so it's hard to say. But if it's something like a 1/2 inch from a 10 inch prop then the difference may not even be noticable. If it's a half inch off a 6 inch prop then forget it. Toss it and get a new one.