What you`re dealing with is an oil stain.
These are easy to remove with dish washing liquid.Simply rub some dish washing liquid into the stain.
Let that sit for about 20 minutes.
Then launder as usual.It doesn`t matter which brand of dish washing liquid you use.
Most people recommend Dawn,
but I`ve found that others work just as well...Joy,
even Kirkland.Dish washing liquid is formulated to remove oil.
Laundry detergent is not.
The dish washing liquid will remove the sunblock.I hope my answer will help you a lot.