Kitchen Aid Dishwasher making grinding sound

I have a 10 - 11 year old KitchenAid dishwasher model # kud24sewh2 that is making a grinding noise when I turn it on. I immediately stopped it and am trying to figure out if there is something I can do without calling in a repair person.

I checked to see if there was a piece of silverware or something else that fell down, but there wasn’t.

I’m not sure if I’m on the right track, but I took off the lower washer arm and outlet. The next thing to remove seems to be the screw for the wash impeller, but it’s a small bolt that I don’t have the right size tool for it. I can’t tell the size by looking at the web site, so I’m not sure what tool to buy to remove it, or if I should bother.

Any info and suggestions would be appreciated. I’m just a novice trying to save some money.
Thanks