Hi there, thanks for asking. This could be
migraine. These
headaches are unilateral in many cases. For you it has involved the left side of your head. However, if this is the first time you are experiencing such a headache, it is necessary to go to a doctor and he should see what is exactly the kind of headache you have. He should also investigate all the possible causes which may cause the secondary headaches. I wish you a good health.