You must wash your hands with soap and water before check your eyes by yourself. You can try to blink your eyes fast, because this can encourage natural tear production. You can flush your eye out with clean water. You can ask somebody to pour the water or solution into your eye with a clean cup. If you cannot remove them out you must seek medical help from your eye doctor. If you experience eye pain and discomfort even after the sand is removed, ask your eye doctor to determine if you have a corneal abrasion which may need treatment.
Dear kid, don't rub your eyes. Ask your mum or dad to take you to see an eye doctor. But if there is much sand in your eyes you can use clean water to wash your eye first, because this can wash out most of them and make you feel much better.