I'm glad you identified your mistake right away and took steps to ensure your patient's safety. Yes, you made a mistake. This is a valuable lesson for you and I hope at your next position you will feel empowered to ask questions and seek guidance until you truly understand what you are doing and why.
At my very first nursing position one of my colleagues (we graduated from ADN school together and we were working on the same unit) made a near fatal medication error with a narcotic. She never returned to nursing. I would encourage you to consider the error you made and ways to avoid similar errors in the future.
Although it has been some time since I have worked in acute care, there were always hard stops before administering high alert medications such as insulin or heparin. Even if there isn't one in your facility it may be wise to consult a second nurse before administering to be sure you are reading the order correctly. I wish you the best in the future. Please never be afraid to advocate for yourself for the education and training you need to practice safely.