I agree you need a safe word, i think we all have been in some what same situation. But you must allways communicate with your patner that there is pleasure pain and pain which you don't like (unless you like it all) your master needs to know your boundries.Because for a Dom and i know i am one ... once your in the element of giving out pain you sometimes forget the boundries of the sub and can cross it. But if you have a safe word then it shall all be fine.