"To err" is to human. We all make mistakes - big or small. What is important is not this that we do not mae mistakes...but its important to accept our mistake..to realize that we were wrong at a point of time and extend an appropriate apology to someone who is hurt due to our wrong deeds and words. Its quite natural to be at the loss of words in such situations.
Not to worry we bring in for you a range of sorry greetings with just the correct set of words to express your pain and apology.