Nrose6

I am a full time nurse in a nursing home and I am responsible for 30 residents. I had a new resident transferred to my floor during the most busy time of my shift over one month ago. I logged in his medications and completed a new kardex on his admission to my floor. Last week it was noted that the date in which he is to receive a 3 monthly B12 injection was not carried forward on the new kardex which was completed at the start of the month by a different nurse (a new kardex is completed at the start of each month) I rang his Gp surgery and tried to find out if they had any information as to when he is due the injection. They could not give me an answer. I then tried to locate his old kardex I had completed which is usually filled away in an allocated space. Unfortunately I could not find this document however I did find a document in regards to this patient which stated we received 5 B12 injections for our stock on a particular date 13.01.17. I read this document wrong and believed the injection was administered on that date and recorded on our new kardex for this month that the injection was due three months after that date 13.04.17. Yesterday I came on shift and siting in my clinical room was his kardex which he was admitted with and the kardex I had wrote for him. These are the documents I could not find last week. His kardex which he was admitted with stated the injection was due on the 7.02.17, I had not recorded this on his admission kardex. Therefore it had been missed and was over a month over due. I informed senior staff and manager of this and was advised to give the injection straight away and send a FBP blood test the next day. An incident form has been completed in regards to him missing this injection. I feel HORRIBLE as it was me who should have recorded on his admission kardex the date in which it was next due. I have been qualified a year now and feel as though I have made a massive mistake so soon in my career. I can't stop thinking about it and feel like a horrible nurse. Has anyone come across an experience like this before? Will my resident be okay? What can I expect to happen in disciplinary terms?