What Does Pressure On The Left Side Of The Head Indicate?

hi so i got a concussion may of 2016, i feel pretty much normal now excpect this weird sensation in my left side of my head. its hard to explain but its like a knot or tightness and i can feel it most when my body temperature elevates like with exercise or when i start to sweat. I feel it mostly all the time but only increases in uncomfortability when im doing physical activity. I feel it when i swallow but in my head somewhere. the right side feels completely fine and i can tell there is a distinguished difference. sometimes if im running and i start to feel it, i have to stop because it starts to feel so heavy and thick. i cant tell if its mucus because im always trying to get it out but ive felt this for about a year and a half (3 months after concussion)