I had umbilical hernia repair surgery a week ago and I have pain in my right side just above my hip for the last 3 days. Should I be concerned?

Probably ok. Did you have a laparoscopic or open repair? Is there an incision near your area of pain? It is probably just muscle soreness after the operation. If you are eating normally, having normal BMs, and no fevers or drainage from your incision then it is very likely normal recovery. Nevertheless, you should see your surgeon to ensure everything is ok.