a thorn in the flesh

We were halfway through the trek, crawling through creepers and thick foliage when suddenly someone seemed to have gripped my arm from behind. It was a moment of shrieking pain followed by an instant cloud of senselessness. I jerked and stopped, tried pulling my arm free of the grip and turned back. A thorn in the flesh had anchored itself firmly in my arm. It refused to yield to my jerk and the numbed senses could not fathom a way out. Liberation from the firm grip drove the instincts and had there been a reasonable object around I would not have hesitated in employing it, snapping the aggressor free. The urge alloyed with a mind in silence created a moment whose memory will forever remain.