You are a PA working in a GP. A 39-year-old male teacher comes to your practice complaining of terrible headaches and is unable to sit still due to the pain. The headache started an hour ago, without any aura/warning while he was teaching. He describes the pain as burning in nature, especially behind his left eye. When asked how bad the pain is, he scores ‘12/10’ in severity. He is mildly photophobic but does not complain of neck stiffness. He looks like he has been crying. He is apyrexic and his BP is 125/80. Upon further questioning, he describes similar episodes 3/52 ago, which resolved spontaneously. What is the most likely diagnosis?