How does an Erratum on one's own paper affect one's career as a researcher?

It will not affect you career. You'll be fine.

An erratum is not a bad thing, per se. Errors happen, and if you fix them it's fine. The error you describe are totally normal and I would even guess that a large fraction of published paper contains this type of error and does not have an erratum.

Even a more serious error that invalidates some of your finding will not necessarily have any impact on your career (but in this case you should write an erratum!). A retraction would be more serious, because retraction are associated with misconduct.

Another point is, that most people will not even notice that there is as erratum for one of your papers.

Let's put it this way: An erratum describing a serious flaw in the paper may (or may not) have a negative effect on your career, but withholding knowledge of such a flaw will have a much worse effect when people find that out.

Also - it's only a problem if the error is such that you should have noticed it and not published the paper at all. Most errors are only seen as an unfortunate coincidence and do not reflect seriously (or at all) on the authors.

A "real" erratum (of the form "this part of my paper was wrong") will not affect your career unless it is about your most important work being all wrong, and all our prestige depends on that single paper.

This may depend on areas, but I would say that an "erratum" of the kind you mention would not (and should not) be accepted by the editor. There are more important things to use the journal's pages for. If it bothers you a lot, include your "erratum" in your list of publications in your web page.