Its nothing serious its called gynecomastia usually in the middle or when starting male pubrity I still suggest to see a GP just in case im 13 and I have the same thing but I think its just normal.
In general terms, gynecomastia is the swelling of the male breast. This can occur as a swelling of the entire breast or, just like the symptoms you describe, simply as a swelling that is restricted to the nipples. The reason for this is due to the hormonal changes that are occurring within in your body due to puberty.
It is likely that, just as one of your nipples already has, your nipples will return to normal on their own without treatment. If would like reassurance or feel that the lump has been with you for longer than you are comfortable with then you should see you GP. You need not feel embarrassed about this, as it is common and your GP will be familiar with this condition from experience.
I also have that they are kinda sore and they are suppose to go away after a few months to a year.
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