Is this early puberty?

Hi ladies, yesterday my six year old sister began to “complain” about breast pain on her left hand side that occurs when she lays on her chest, or takes any deep breaths. During the past 3 months, she’s gained significant weight after a change in routine during quarantine.. as most of us have. She has no other hormonal changes but I’m just curious before we run to the ER when my dad gets home (because the pain is making her cry) is this something that normally happens? There’s no family history of early (precocious) puberty. What can we give her to make her feel better? Is the trip to the hospital necessary?

She turns 7 in August. We are African-American. If any of these factors matter. Thank you all in advance. We’d just like to soothe her pain in the mean time.