Getting constant throbbing pain top left hand side of head. it comes on during day & disappears at night. diagnosed with tension headaches. tumour?

No tumor likely: Especially if you feel nausea and/or light sensitivity, this can be migraine. It's a vascular, not a tension headache or a sinus type. A tumor would not go away at night nor would it be likely to pulsate. Don't be afraid - do see a Dr for exam, eval and Dx and Rx. I hope it goes well. Acupuncture can help too.

Likely migraine: Sounds like this is pretty scary for you. Throbbing headache on one side of your head that gets better with lying down in a dark room is often migraine. However, if this is new and isn't going away you might need an examination. I hope that helps!