Does Popping a Pimple Break Your Fast?
Question

I have pimples on my face, and I burst one of them whilst I was fasting during Ramadan. I was not sure whether that broke my fast, but I made up that day afterwards. Do I have to do anything else?
Praise be to Allah.Bursting pimples that appear on the face does not invalidate the fast and does not require that day to be made up later on. 
What breaks your fast
The things that invalidate the fast are well known and are indicated by the Quran and the sahih Sunnah of the Prophet (peace and blessings of Allah be upon him). They are as follows: 

Intercourse
Masturbation
Eating and drinking
Things that take the place of eating and drinking, such as injections that provide nourishment
Vomiting deliberately
Cupping and things that are akin to it, such as donating blood
Menstruation and postpartum bleeding in the case of women

Does popping a pimple break your fast?
It is not permissible to say that this thing invalidates the fast without sound evidence to that effect, and there is no evidence that busting pimples or boils that appear on the body invalidates the fast. 
Based on this, your fast is valid and you do not have to make it up, but you will be rewarded for the day which you fasted to make it up, and that will count as a nafl (supererogatory) fast on your part. 
It should also be noted that you should refer to a doctor about bursting these pimples to find out whether it is harmful or not; if it is harmful then you should not do that. 
And Allah knows best.