iphone6 requires code because of 48 hours, but I used it only 8 hours ago

My iPhone6 (updated to iOS9 last weekend) requires my passcode because of the 48 hours. But I used it only 8 hours ago. Has my iPhone been hacked? I am very afraid to enter my code now.

I have only downloaded apps from the Apple app store, never from the internet. Sometimes I open .doc or .pdf in my mail on my phone, but only if I know the sender and I expect something like what was sent.

Please let me know if I can securely use my phone...