The wood will probably not change the pH much, but it will deplete soil nitrogen for awhile as it decomposes. Compost and/or fertilizer would be a good thing if you plan to plant in it. Unless it is mostly fresh wood chips, you could probably plant now. Just keep an eye on your plants for nitrogen deficiency and give them some liquid fertilizer if it appears.

Actually, you need to add "greens" containing nitrogen to help the fresh wood to break down. Coffee grounds, fresh grass clippings, even urea fertilizer can provide N.
I wouldn't replant until a lot of the wood has broken down since it steals N from the soil during the wood decomposition process (and keeps it from plants).
hortster

How deep did they grind it?

You may be seeing that Willow again.

One that I grew up with was cut down about ten years ago and the stump ground.
Now it is back and about twenty feet high.