I have a small tender spot on my left side of my head whenever i run my fingers through my hair? feels a bit achy. what is it?

Hard to say: How long have you had it? Sometimes we just bump ourselves, don't remember and then notice it later. So it could be that. Can you have friend/family look at your scalp to see if they see a scratch/bruise/lesion/ulcer etc? Do you feel a mass? If it's not better in a few days - see a doc. Go ASAP if you have vision changes, lightheadedness, headache that won't resolve, weakness, slurred speech.