no worries—(Austral. coll.) that’s OK; no problem (used as an expression of reassurance):
- She asked me whether she could stay in my place during her stay in Singapore. “Sure, no worries,” I said.
not to worry—(coll.) is used to say that smth. need not be a cause of concern:
- The government had no money, but not to worry, he said, because he had private friends who would foot the bill.