Career effect of embargo on doctoral dissertation
I do not see that embargoing your dissertation will have any consequences for your career. Until recently, theses and dissertations only existed in hard copy: at least in the sciences, people expect to read your papers and not your thesis. In all likelihood, nobody will ever notice that you've embargoed it.

In any case, placing an embargo on the thesis just prevents the university library from distributing it. There is nothing to stop you sharing a copy with someone (e.g. a potential postdoc supervisor) if you wish to do so.