Well this is a common situation and frankly one for which there is no scientific answer. There are individual reports that breast and nipple massage has caused increases in size, the problem with this is that extended nipple stimulation almost always leads to some level of sexual arousal and sexual arousal causes breast engorgement in a significant percentage of women - some may see as much as a cup increase from blood flow with arousal and this will not last more than a few minutes to a few hours.
On the positive side it will not harm you to use some oil or lotion and massage your breasts and especially you nipples - from what I have read it seem pinching, pulling twisting motions while tugging outward is what is supposed to work - the idea is to get hormone release like nursing women do so the nipple stimulation is similar to a nursing baby . Be sure to use a lubricant or you will have very sore nipples. I doubt it will do anything other than perhaps arouse you but other than a little soreness I do not think it would harm you either