Larry Johnson Fight -- VICTIM'S GRUESOME INJURIES ... 'He Sliced Me With Broken Glass'

The man who claims he was attacked by ex-NFL star Larry Johnson says he needed 7 stitches to close up a BLOODY GASH on his arm ... after Johnson sliced him open with broken glass.

We broke the story Johnson was arrested for attacking another man inside the Delano Hotel in Miami Beach early Tuesday morning ... and now, TMZ Sports has pics of the alleged victim's injuries.

"He wailed on me for a good two minutes before security came over," the man -- who asked to keep his ID private -- tells us.

"I couldn’t get back up on my feet – so it wasn’t even a fight. He just wailed on me – and used a tall broken vodka glass that got knocked over when I fell down [to attack me]."

The man continues ... "I was able to cover my face – but I’m covered in cuts on the side of my neck, cut the back of my hand, and had to get 7 stitches for the gash on my arm."

The man says he had NEVER met Johnson before the incident -- despite reports to the contrary -- and says he has no idea why LJ would attack him in the first place.