Does popping a pimple during Ramadan, while fasting, break the fast, necessitate making up that day, and require atonement?

Popping acne does not invalidate the fast and does not necessitate making it up. The things that invalidate fasting are specified in the Quran and Sunnah (definition), and they are: sexual intercourse, masturbation, eating and drinking, what is considered to be in the meaning of eating and drinking (such as nourishing injections), intentional vomiting, cupping and what is considered to be in its meaning (such as blood donation), and menstruation and post-natal bleeding for women. There is no evidence that popping acne invalidates fasting, and your fast is valid, and you will be rewarded for your fasting as a make-up and it will count as a supererogatory act for you. It is recommended to consult doctors regarding popping acne to know the extent of its harm.