Newgradacutern

I am freaking out and need some perspective. I am new grad nurse, day 2 on the unit in ED. I did my pregrad in the ED at another hospital that was really tight for resources, which meant I learned a lot of really bad habits and shortcuts that I realize are not best practice. Anyways- Our patient got an order for 20meq/L KCl in 1 L D5W. I went and grabbed the bag, and a practice I picked up from the previous hospital was to hang KCl by calculating gtt/min instead of using the infusion pump since we just didn’t have any on the unit. Unfortunately, this stuck in my brain due to the number of times I did it that way, and I did it for this patient. The nurse I was shadowing was not there when I hung the bag, and to my luck it was the charge nurse that caught my error, within minutes of me hanging it. She briefly told me it was a really big mistake, that I could lose my license over it. She then filed an incident report and emailed the manager without offering any follow up, education, or to even hear why I made the mistake. I overheard her gossiping about the incident in the break room, stating she is worried for the future of nursing after dealing with so many new grads. I am distraught over the consequences of this, and fearful of not only being labeled as incompetent but also losing my job, and my license over this. I have no idea what to do with myself I am a wreck. Thankfully the patient is fine, she only received about 75 mls before the pump was added. Any perspective on being a new grad and dealing with making errors and mistakes would be welcomed, and any insight on the types of consequences that are likely as my brain just keeps going to being fired/losing my license.