Did you provide an email address for the account? If you did, you should be able to request that send a new password is send to that email address at the log in page. If you didn't provide an email address, bad luck; you won't be able to gain access to your account. However, you can create another account, and using that account, edit your old account's userpage to mention that you no longer use it. Before creating the new account, please read up on Wikipedia's username policy, to make sure your account complies. Hope this has helped.
