It’s OK to Make a Mistake
Your company will expect you to make mistakes. That’s life.
It’s also how you learn.
Repeating the same mistake will concern your manager more.
Not “fessing up” to the mistake will be taken as a bigger strike against you than the mistake itself.
I’ve seen staff cover up, lie, and blame others. This enhances a blaming corporate culture. (Not where you want to be!)
Most companies want the issue fixed professionally, quickly (now if possible), and handled better the next time. Blaming someone else accomplishes none of these things.
Collect major points if you say: “Sorry. I screwed up. I made a mistake. It won’t happen again!”