Apologies are broad justifications and excuses offered up to large audiences. An apology is frequently used to emphasize recipient perceptions and divert attention away from an act itself. The most obvious example is when ‘I apologize’ is followed by vague descriptions of behavior.
“I apologize for my actions yesterday.”
Sorry is used to express personal feelings of sorrow and regret. Saying ‘I am sorry’ can also imply a desire to be forgiven by individual recipients, especially when behaviors are clearly communicated.
“I am sorry for ignoring you last night.”
Simply stated, an apology is not necessary for clearly communicated sorrow.