Did you configure the device to use TACACS only? If you did not, you can probably gain access by taking the TACACS device off line (or preventing the access point from connecting to it in another way). Once the TACACS connection fails, you should be able to use your local credentials.
If that doesn't work, or if you have configured TACACS only, you can try using a console connection to the device. Hopefully, you didn't turn it off. Using it you can switch the authentication back to local.
As a last resort you can just look up the password recovery instructions for your device. Usually that involves a console connection and interrupting the boot sequence.
