That may well be a problem, Microsoft doesn't provide password recovery for Access:
"It is critical that you remember your password. If you forget your password, Microsoft cannot retrieve it. Store the passwords that you write down in a secure place away from the information that they help protect."
You'd be in the realms of 3rd party utilities, a quick internet search for Access Password Recovery Tool will show some products that are available that supposedly recover passwords.
Unfortunately, it may just be a case of starting again with a new database and recreating the contents.