That depends...it depends how long ago you took these classes. If it was recent, like two years ago then perhaps taking upper level courses would be the best thing. It also depends what your version of bad is, is bad a B, or is bad a C or D.
If its a B, then no. I wouldnt retake it. It ifs a C, then perhaps. However, if you got a C in organic, then I would say, unless you plan on taking something like P-Chem to compensate for that poor grade, then I would retake organic. No pont in taking any higher chems past orgo I and II.