??? difference ???
I am not a teacher of English neither a native speaker.
To be sorry for means to feel pity toward someone. Example: I feel sorry for whoever marries him! I am sorry for your loss.
To be sorry about means an apology and is used in the informal, casual situations. For example, earlier this afternoon I was in a restaurant and happened to be seated at the filthy table. A waitress cleaned it up and said, "I am sorry about that."