In a recent interview I was asked to rank my skillset on a scale of 1-10. In an attempt to not sound pompous, I gave 8s where I feel I could have said 10. Could this have been detrimental? What is the right way to respond?

If there were a very specific context and definition of the expected skillset one could have done its own avaliation and define the grade.

If there were a very specific context and definition of the expected skillset one could have done its own avaliation and define the grade. Otherwise, it does not sound like a good interview question.

Anyway, considering that no one can be considered 8 or 10 or 0 at all skills that define a professional, the answer could be followed by a more in depth explanation on what you area really good on and why you consider that (usually with real cases/achievements backing your thoughts)

Any answer (8, 10 or 0) without context can be interpreted in so many ways that it is impossible to say what will be the outcome of the interview.