While good is often used in the sense of well, as in:
We are all good; thanks for asking.
It doesn't work in your sentence; you need to use well - and the use of myself, while legitimate for emphasis, is unnecessary.
Moreover, to nail something in the sense of achieving/accomplishing it is slang. So it's fine in certain contexts and dubious in others. In short, you might rephrase as:
I was surprised (myself) at how well I nailed the interview
or, more formally:
I was surprised (myself) at how well I did/succeeded in the interview.