obviously i cannot examine you son but he most likely has adolescent gynecomastia. a hormonal side-effect of good 'ol puberty. yes these can be tender. ibuprofen may help and obviously he should avoid trauma to this area or trauma from teasing brothers/friends who like to pinch them or give him a painful "twister" or "purple nurple". (ask you son and he will explain what this is). these things can add to the normal discomfort of course. research adolescent gynecomastia on the internet. if you are concerned you can see his regular medical provider for a consultation.
my 13 yrs old son has a lump on left breast near the nipple area and it is causing a lot of pain what should i did