Can I repurpose pine tree stump grindings
Depends.  I use substantial amounts of chipped wood in my tree farm operation.  I find that I like to wear gloves working with it because the ends are sharp, and it's a source of splinters.  It's painful to walk on barefoot.

If you use it as garden mulch, it should be composted for about 3 months first.  Pine in particular is loaded with terpenes which is tough on other plants.  3 months kept damp and the terpenes decompose or leach out.

If you have a garden plot, or an annuals bed, compost it for one season, then spade it into the plot.  Wood chips hold moisture and will reduce the needed frequency of watering.

Do NOT use it as a thin layer in muddy areas.  It mixes with the mud, and you end up with a region that never dries out.  If you wish to use it this way, put down a layer of geotextile first, then put a layer of wood chips on that.

You can also just spread it out with a rake, and after a rain go over it with a roller.  It will gradually decompose into your sod.