The easiest way to do this is have a field that flags that the T&Cs have been accepted.
So when a user creates the account you set this field to 0 and on login you would create a redirect based on the value of that field.
So if the field equals 0 then the user is redirected to the T&Cs page. The T&Cs page would actually sit in a form with the tick box and the submit button would trigger the update record behaviour which would change the value of the flag in the user record to a 1.
That way, the user will never get redirected to the T&cs page again.
However, a much tidier way of doing this would be to get the users to agree to the T&Cs during the registration process. Otherwise you could potentially end up with a load of user accounts that haven't agreed to the T&Cs which means housekeeping for the site owner.