Hi, I Have A Twinge Of Pain That Hurts But

hi, i have a twinge of pain that hurts but almost feels like a twitching nerve ( dont know how else to describe it -- just how fast it happens then is gone again.) i noticed it all day off and on only on the left side. when i run my fingers over the area, it feels almost like a bruise and hurts when i try to put my hair into a hair elastic, from tugging only in that area. what could be causing this?
thanks- kaitlyn