does it have a changeable combo? If so you may have accidentally changed the combo while locking it up. (usually theres some sort of ring you have to twist to change the combo) If you did that, you most likely just changed the last digit. Try all of the digits on the last combo ring and see if that helps.

If it doesn't, grasp each end of the cable on either side of the lock, and pull. While holding the tension , rotate the combo rings one at a time until you feel them click, keep doing that for each one. Sometimes you can "pick" them that way. Kryptonites are nicer, and Ive only done it on my gf's cheapo combo lock. YMMV.