Assuming security is set up properly, you can't do anything.
Try creating a new db, then importing all objects to the new db. DISCLAIMER: you will lose some information, such as relationships window formatting.
If that doesn't work, then it's probably secured properly. There are Access security cracker programs that work. Talk to your supervisor about buying one, or maybe you can find one for free. I haven't tried.
But without further (external) help, you're stuck.