Sushi is best eaten fresh - you'll probably get sick....so throw it out, we don't need you sick when we play nurse and patient.
Now for a breakdown of what sushi is:
Sushi refers to the actual rice - believe it or not. Many ingrediants from raw fish to vegitables are then added to it.
Sashimi is just the plain raw fish, usually Tuna, Salmon or sword fish
Nigiri is a roll of rice with a slice of raw fish or steamed prawn laid on top.
Then you get the various 'rolls': Californian, rainbow and maki, salmon roses (too die for)
I LOVE LOVE LOVE sushi, I"m going on a sushi making course next month! Will take photos