I'm afraid you have to either retrieve your password by logging into Google, the phone prompts you to do so. Or if you have configured a Samsung account login to Samsung dive website and you will be able to unlock it.
Lastly if the above doesn't work, say goodbye to your apps and contacts and other data by resetting the phone. Switch off your phone, press volume up + home key + the power button at the same time until the phone lights up and release the keys. The phone will boot into recovery mode, look for the option that says wipe data/factory reset or something like that and use the home button to select. U scroll down the screen using your volume keys. Good luck there.