Use the Sign-in Helper to get back into your account using your Yahoo ID, mobile number, recovery phone number, or recovery email address. If you forgot your password, be sure to change your password to a strong one that you'll remember after you're in.
If you don't have recovery option(s), probably you will not be able to sign-in your account.
From Yahoo! Help:
If account recovery information is incorrect:
We take your privacy and security very seriously, and only let you reclaim an account if you prove you're the rightful owner. When you register for an account, it's up to you to provide valid recovery info that proves ownership. The best way to safeguard your account access is to update your recovery info whenever your mobile phone number or email address changes.
Sign-in Helper can't recover your account online:
We need valid security and recovery info to protect your account. If you weren't successful with Yahoo Sign-in Helper or the other options above, you likely won't be able to recover your account. If you remember your sign-in information later, you can come back and try again.