Are you trying to log in remotely to the device? The error you're getting is that the shared secrets (i.e. password) between the device and the ACS server is wrong. So, the device can't authenticate. No authentication, no access.
If you have aaa to do tacacs first, then local, and the device is connected to the network, it will continue to attempt to authenticate to tacacs. It wont let you use local.
Try and disconnect the uplink to isolate the switch, then use local admin. It will see that tacacs isn't available, and go to the local admin account. But only if you have it set up right.
Otherwise, password recovery is your friend..if you left it turned on :)