well I am extremely sorry that you have permanently injured yourself in chasing this twerp
Is it intentional injury on the twerp's part - the difficulty is taht you chose to chase the fella. The leading case is Letang V cCooper 1965
http://en.wikipedia.org/wiki/Letang_v_Cooper
the alternative is an action in negligence. The difficulty here is that the leading case is... letang v cooper and twerp if you think about it, wasnt really negligent
the next difficulty is causation - but for the twerp smashing your window you would not have suffered injury - but oops you fell over....
so the but-for test isnt fulfilled
things are looking bad for any civil action I think