My phone got locked how to unlock without erase data

OK....You or someone else entered the passcode incorrectly too many times. If you know the correct passcode, you can wait it out and then when prompted, enter the correct passcode. If you simply don't know the correct passcode, there is no choice other than than to erase the phone, which will wipe all the data off the phone. If you've been backing up regularly, you can then restore the phone from a backup after you get back in. If you haven't been backing up, your data is gone.

See the directions in this link --> If you forgot your iPhone passcode - Apple Support

kabir186 wrote:

What is the meaning of null ?

Typically, the message will specify the number of minutes, hours or days it might be before you can try to enter your passcode again. I've never actually seen "null" shown. The reality is you either wait it out or you erase your phone and wipe your data.

Locked how?

Did you forget your Apple ID?

Did you forget your Apple ID Password?

Did you forget your Passcode and if so, does it say Disabled or Unavailable.

kabir186 wrote:

I do remember my passcode my son locked my phone by mistake

Then wait until you're given the opportunity to try entering the correct passcode.

The message on your screen suggests you will be able to enter your passcode. I just don't when you'll be able to do so.