Far out dude that must have hurt. Im guessing you sustained a severe blow to the back of the head? That is where your occipital lobe of the brain is, it is the one that processes all the visual stuff. I knocked myself blind when I fell off a bike as a kid, seriously not nice, it didn't last more than 30 min though.
Re DMT & blind people, 25% of your brain is designated for visual processing, that is a lot of brain sitting idle waiting for input. I would put money on a blind person seeing during a spice journey. I know most of mine are experienced with my eyes closed and I am sure the visions have little to do with how the eye works. Its all neuronal firing, an avalanche of chemical stimulus.