Hi Raymond,
Similar situation happened to my windscreen last July too. Parked beside netball court in school, kana small cracked on windscreen abt size of 50cent coin. Initially thought its nothing but once travelling along expressway for 90km/h+ can literally see the crack 'growing' and hear soft cracking sound.
Kan cheong, so I sent mine to a workshop@eunos that deals with AIG, paid $100 + 7%GST excess. Won't affect our NCD, but paid additional for my V-Cool cos cant claim

Anyway, better safe than sorry u should replace your windscreen.

Thank Pizzaboy and Silver for the information.
Call AIG to report this crack this morning(since now need to report any "accident" with 24hrs but for my case consider act of god, since dont where the sand or stone come from) was told the same information. I only need to pay $100 + 7% GST for the Excess and that exclude the solar film which i need to pay additonal.
Really unlucky for the incident. Was worry whether to pay myself to replace or claim insurance due to my high excess.