We caught up with the "Catfish" star on "TMZ Live" Monday -- Nev fought back tears while recounting the aftermath of his brutal crash ... noting he is lucky to be alive.

As NS put it ... his medical team at Stony Brook University Hospital were shocked that he was even able to move following his surgery ... since they expected him to be in a far worse condition, given his injuries.

Nev, who was hit by a truck two weeks ago in Long Island, NY, while heading to his son's school on an electric bike, revealed he doesn't recall much from the actual accident itself ... but knows the incident could have been prevented had there been a bike lane in place.

He added ... "The roads need to be shared. Cyclists and runners -- which is really what I am more than anything -- need to have better space that's designated because ... there's just not a good system in place that keeps everybody safe."

He is now on the road to recovery ... however, Nev said the experience has been "a real lesson in patience and humility."

Nonetheless, he told us he's as determined as ever to still compete in the Honolulu Marathon in December. His bottom line was clear ... he's planning on making a "big comeback."