Nine times out of ten, the reason your bottom bracket will be creaking is that the bearings are moving. This creaking sound is going to be because of movement so that you can count on that. Anyway, unless you are proficient when it comes to bike maintenance, you may want to seek help from a reliable outside source.
Some people will lubricate the bearings to fix the issue. However, this is only a temporary fix and can often make matters worse. The safe bet is to address the problem as soon as you detect it.