Ok, try this. Type in the following in your web browser:
http://mail.yahoo.com then press enter.
Next look down toward the bottom where it reads
Keep me signed in and go to the next block where the Sign In button is located. Look slightly down and to the left you will see a hyper link with the phrase:
I can't access my account. Click on that and on the next screen select which one you think is the correct reply.
My question to you is are you sure you typed the yahoo id in correctly? If so then it may be you typed your password in improperly. Either way, follow that second page and see what happens. I am sure that Yahoo support will help.