That's unfortunately, but no worries. This is what you can do:

1: Recover you password

1. Enter your e-mail address

2. Klik on recovery link in the e-mail (didn't you get the e-mail? Check your spambox)

3. Enter a new password

4. Login

2: Check your e-mail address

Is the e-mail address you are using to login, the same as the one registered with your account? This can happen if you login with Google the first time and try to login with Apple the next time.