No, getting a cramp will not trigger you to have a period. If you get a cramp when you aren't scheduled to have a period, it is probably a muscle cramp and should be treated by stretching or application of cold, whereas menstrual cramps should be treated with painkillers or a hot bath. If you get cramps regularly when you're not menstruating, it could be a deficiency of potassium, salt or water, and you should probably see a doctor.