Not necessarily more than once. It could, like you say, be a sentence expressing a habit, or it could be a recounting of a story: the police checking the facts "so tell me again, he goes to the kitchen to prepare onions, but he hurts himself with the knife, that's when the burglar, aka the ex-wife, panics and jumps out the window only to fall into the neighbour's bouncy castle, making yet another clean getaway, whilst the victim falls into yet another accidental scrape"... For example.
In English if you cut yourself in the kitchen accidentally you would say "I hurt/cut myself on a knife" - "I hurt/cut myself with a knife" implies you did it deliberately (hence all the comments people have posted about it being a dark expression). Is there a way to make a similar distinction in Italian or is con used for both cases?
You have to distinguish between:
fare (del) male a qualcuno = to harm somebody. Usually physically (without del) or psychologically (with del). (del is kind of "some").
farsi del male: to damage oneself. For example, by smoking.
farsi male = to get hurt
fare male = to hurt. As in some injured body part:
My leg hurts = la gamba mi fa male. Notice that you have to use mi = a me (ti = a te, gli/le = a lui/lei, ci = a noi, vi = a voi, a loro).
You don't use personal pronouns when you mean some situation is painful, as in "It hurts to be betrayed" = "Essere traditi fa male".