Part of the dip will be secondary to loss of cartilage underneath, and likely that cartilage loss has affected the growth of your nose as well. There are two basic approaches. One is onlay grafting where cartilage is placed in the dip, which sounds like what you have had done. It is a camouflage technique. The second, newer method is to rebuild is to rebuild the top of your septum ("dorsal strut") with rib cartilage, which returns your nose to a more normal shape and function. You would need to find a surgeon with significant experience in open approach nose surgery, particularly revision surgery.