You don’t say much about your concern, but if you have a lump under your nipple, it could be one of two things. It could be
an infection or a condition called Gynecomastia, which is common in young boys going through puberty.The swelling under the nipple can last for a while,but will eventually disappear in a few months without any treatment.
The reason for this is "hormonal changes" in young males and nothing to do with breast cancer.
Please talk to your mom or dad to take you to your family doctor just in case you have an infection that would need to be treated.However, if it is Gynecomastia,your physician will be familiar with this condition from experience and can reassure you that there is nothing wrong with your breast okay?