There's a way to create a new account without knowing the password. 1. BOOT INTO SINGLE-USER MODE
Turn on the computer. Upon hearing the startup chime, hold the key combination CMD+S. This boots the computer into single-user mode, which in turn gives you access via the root user. It is important to note, however, that this can be blocked by a firmware password. If that’s the case, theres other guides on getting into single-user mode while locked.
2. MOUNT THE HARD DRIVE
Once single-user mode boots (it should look like a black screen with white text), we need to mount the hard drive. At the prompt type in:
/sbin/mount -uw /
3. REMOVE THE “SETUP HAS BEEN COMPLETED” FILE
Now that the drive is mounted, we can edit the file system. We’re going to delete a file that tells your computer that you have completed the initial setup. Type in:
rm /var/db/.applesetupdone
This command deletes the file “.applesetupdone” in the /var/db/ directory, which the computer checks for on startup to ensure that the computer has already been set up.
And you're done, you should be at the new user creation screen when you're done