NodeJS/Express + HTTPS: How to deploy key & certificate to AWS EC2 node?
It is not recommended to keep secrets on EC2 instances. You may use AWS KMS to keep the secret keys and AWS Certificate Manager to manage your SSL certificates.
You could setup a Elastic Load Balancer(ELB) in front of your EC2 instance and have your SSL certificates applied on the ELB. Here is a guide. It is good practice to terminate SSL at ELB level to take some load off the server on your EC2 instance.