If i gave oral when i had a cold sore that was already healing, what is the percentage it may be passed on?

No exact rate: There is still a chance of passing hsv1 in your case (cold sore herpes). I wouldn't recommend you do this again from the time you feel the lesion is coming on until after it is resolved. If this isn't an option use a condom if the oral was performed on a male or a dental damn if on a female. Non genital herpes, while less painful is still unpleasant.