Hi Olivia,
How are you? One-sided headaches may be caused by primary headaches such as migraine headache. It usually presents with throbbing headache and sometimes nausea, vomiting, sensitivity to light and sound and even numbness. This can also be associated with hormone changes which can be associated with your age. Rest, ice pack and prescription pain medications may help. If it persists, have this checked by your doctor for proper evaluation. Take care and do keep us posted.
Tell your mom or dad to take you to the doctor.... It could be nothing or a underlying isse of somthing worse.