Um... well i would just be honest with them and tell the truth. Or you can explain what happen and just be honest and that wont get you in any more trouble if you know you are doing to "bullying" is when you pick on another kid and you get caught but if u were than no matter what you will get in trouble.
If the 'something bad' involved bullying .. then you're not going to get a lot of sympathy here. There are consequences for your actions .. and you deserve it. There is NO excuse for bullying .. even it was only just a little bit.