Will germolene hurt when applied to a burst & infected spot? and how long does the pain relief take to kick in?

Germolene does not provide any pain relief, it is just an antiseptic compound and you use it to clean the cut or wound for preventing superinfection. If the spot which I assume a boil bursts, applying Germolene does not bring any extra benefit because the lesion was already infected. You just need to clean the spot and put a dry dressing on, keep it clean and change the dressing daily.