create sql server login for own domain account
This requires stopping and starting the SQL Service, but will get you access to the SQL Server Instance if you are a local admin on the server.

Run this from an elevated command prompt.

Substitute the service name for mssqlserver if you have a named instance or SQL Express i.e. mssql$sqlexpress

Substitute your domain and account name for BUILTIN\administrators if you do not want to grant sysadmin for all local administrators and want just your account.

Note: the /m SQLCMD switch is single user mode and only a SQLCMD connection will be accepted. This is to keep from being locked out by a service that connects before I can get connected.

I have put these commands in a .bat file and ran it from an elevated command prompt. That makes the outage very short.

As always, test on a dev instance before you go running against production.

net stop mssqlserver

net start mssqlserver /mSQLCMD

sqlcmd -Q "if not exists(select * from sys.server_principals where name='BUILTIN\administrators') CREATE LOGIN [BUILTIN\administrators] FROM WINDOWS;EXEC master..sp_addsrvrolemember @loginame = N'BUILTIN\administrators', @rolename = N'sysadmin'" 

net stop mssqlserver 

net start mssqlserver 

sqlcmd -Q "if exists( select * from fn_my_permissions(NULL, 'SERVER') where permission_name = 'CONTROL SERVER') print 'You are a sysadmin.'"