I forgot my passcode after change the code
I forgot passcode on my Iphone
Click on the following and read the instructions there: If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support
Also note the following from that support article:
You need a computer to follow the steps below. If you don't have a computer, borrow one from a friend, or go to an Apple Retail Store or Apple Authorized Service Provider.