Any increase in breast size is usually your body's response to estrogen and would be temporary if it's caused by the pill.
It's also common for breast size to fluctuate during your natural cycle and throughout your life. Changes in weight, pregnancy and hormone levels etc can affect it :)
Try not to worry about it, and enjoy them as they are! I wish mine didn't get grow as big as they did (naturally due to weight) because mine dropped so much in size (F to B cup) that they sag to below my ribs and Im only 30 🥲 Having bigger boobs isn't fun either- the backpain, tenderness, expensive and "ugly" bras, lack of pleasure sensation, and difficulty finding well fitting clothes without tailoring.
Now just looking forward to becoming pregnant and hopefully being able to wear some of my older lingerie 🫣