Lightheadedness and back pain after cut

it sounds like your cut triggered a panic attack and a vasovagal attack; in short, for whatever reason you got freaked out and fainted and have had some ongoing panic and anxiety associated with the experience (which is normal).

i feel like what you're experiencing is a state of "hypervigilance", where you're monitoring even the smallest changes in your body and noticing them where you wouldn't have noticed before. focusing so intently on the goings-on of your body can cause you to feel normal sensations even more strongly than if you ignored them -- also, because you're so focused on feeling every little thing that seems unusual, your muscles are responding by tightening up and tensing up and you ache. and certainly, you're feeling panic or anxiety that "something is wrong". its likely that nothing is wrong at all; you are just feeling residual panic from your fainting episode and are focusing so much on every thing your body does that you are convinced something is wrong.

My recommendation is to try relaxing, breathe deeply and slowly, have confidence that nothing is wrong -- and really, if something was badly wrong you'd have something serious happen and you'd end up in the hospital.

you should go to a "walk-in" clinic -- for about $100 you can be seen by a doctor who can check on you, and in all likelihood reassure you that nothing is physically wrong, and explain how panic, anxiety and PTSD work.