i was hand feeding my fish today and i noticed my koi on his left side near the end of his stomach had a white spot bout size of a dime. looks like couple scales missing, spot is protruding a bit like its a sore. its not red or pink at all its completely white but some of the scales that are there are still orange. what is this? i thought maybe he scratched himself on the cinderblock i had in there so i took it out. he likes to hang out in the cinderblock alot. should i just let it heal on its own or should i hospitalize him?