Hi. In addition to the above suggestions, I have found the following webpages for your references:
4) dict.leo.org/ende? search=don't+care (be sure to delete the space after the question mark when pasting on address bar)
I also remember a phrase of "sich(Dat) keine Sorgen machen". However, I do not know if this actually means "not to worry" rather than "not to care".
Anyway, take care. / Mach's gut!