Had Kenalog injection 4 years after rhinoplasty and I have a dark discoloration on nose. What can I do?

Without a photo it's impossible to say for sure. It's unusual for a steroid like Kenalog to cause darkening. Interestingly, it can sometimes cause just the opposite: a temporary loss of pigmentation. Could it be a bruise from the shot? Pictures would really help here, but ideally you should discuss it with your surgeon.All the best,--DCPPearson Facial Plastic Surgery®

Without the benefit of physical exam,and  photos- it's difficult to give the best answer . The dark spot could be one of several options. This must be discussed with your Surgeon ASAP.