Links in this existing thread on how to redo CO edge. The feasibility will depend on your st patt but if only removing/redoing the ribbing it's usually very workable.
What CO did you use originally? Did you use a smaller ndl? Is the rib elastic but not the CO edge?
ETA: if you opt to cut off the ribbing and work back down, you can then adjust your BO edge to be as loose/snug as you want (several BO options to choose from).