As a clinical leader, one of your most important duties is to ensure that all organizational policies are followed. Make sure you are very familiar with them so you can interpret them for subordinates if necessary; application of heat without a physician's order is probably covered in those policies.
Some state BONs, including mine, have specific guidelines about when a new grad can assume a supervisory position without immediately available backup from a qualified RN. Make sure you are familiar with yours. It goes without saying that you should also have your own liability insurance
if you are in a nursing leadership position.
You should be provided with additional training to prepare you adequately for your new leadership position. As the 'senior' person, you will be making decisions that not only affect your patients, but also the organization. Some of these decisions can have significant consequences in terms of liability. If your organization is not providing any training, find out if they will pay for training from an external source. The higher your position, the greater exposure to personal
liability you will have.
Trust is an essential component of the relationship between a leader & subordinates. I encourage you to focus on developing this as your first priority. As the 'only' RN, you also need to make sure that your actions show that you respect and value the contributions of other members of your team.
Best of luck to you in your new role.