No worries at all. What version Facebook application are you running? You can try to uninstall then re-install the application and it may help reset it to where the log in information is now correct. Sometimes the applications save information and no matter if you change the password or not it still submits the original password. Once you do this it should resolve your problem. Hope this helps.
Have you tried to delete the application and re-install it? The steps are below. Hope this helps!