What is the credit report damage from a student loan delinquency?

Long story short, I have been paying a loan institution every month well over the required minimum payments (I have several student loans with this institution), but due to a very stupid mistake on my part thinking the loans were consolidated, I had a loan delinquency on one of the loans for 9 days before I got a notice about it and paid more than the required payment immediately. Because I have been paying consistently to this loan institution for the past several months, is there a way to get this fixed somehow? I am uming no at the moment. Does anyone have any idea how badly this will affect my credit score?