Short bio for thesis back cover?
It sounds like you're thinking of your thesis like a book, and indeed in some countries/disciplines, at least a few copies to get produced as such.  

For most theses that I see these days, however, the notion of "back cover" is entirely meaningless.  There is an electronic document that starts with a cover page, which you might consider a "front cover" if you want to, but the end of the document has nothing in particular to distinguish it, except that you come to the end of the references and/or appendices.  Moreover, many institutions have fairly strong requirements for thesis formatting, and in most that I have encountered there is no place for an author bio.

As such, I think that adding an author bio would not make sense, unless it is specifically part of a format that you are required to use by your institution.