Little bump/lump

So, a wk ago i was changing my daughter( who is 6yrs old )into her pajamas, when she took off her shirt she said her right breast hurt when she wears clothes. So i checked her and i felt this little bump right in the middle of her breast. Its only on her right side , i did ask my aunt which is a RN and told me it was totally normal for little girls to start “developing” i guess at that age but to still take her to her pediatrician, i want to know if ya’ll mommies have gone through this with your daughters at that age, what to expect, what happens next ect