You need to get some oil into this chick ASAP. This can happen with a very young chick because their digestive system is still immature. Chicks can be real pigs to their downfall.
I recommend coconut oil since in its solid form, it's easier and safer to administer than liquid oil. Give a teaspoon of oil by prying open the tiny beak and putting tiny bits of the solid oil on its tongue.. It will automatically swallow. Gently massage the crop after you get a full teaspoon into the chick. Wait a half hour and give another teaspoon of oil and massage again.
You should be able to feel the contents break up and start to empty.
It would be a good idea to get some proper chick grit as your sand may be too fine for this purpose.
There is a risk the impacted crop could proceed to constipation. You'll know if this is happening if your chick gets lethargic and droopy, eyes are red-rimmed and dull, and stops pooping. Give it more coconut oil as soon as you notice any of those symptoms since constipation kills a chick very quickly.