I need to access an SQL server behind a router from an AWS EC2 instance.
Is it reasonably safe to open a port on the router if I am white listing the IP of the EC2 instance? 

If there is a best practice for this, or if anyone knows of a procedure for this any references are welcome!

SQL server OS: Windows Server 2008 R2 on domain controlled network
SQL Server version: 2008 R2 SP3

AWS EC2 instance OS: Ubuntu 18.04

Intention: Access SQL with sequelize on an expressjs based web server