Louis Nix III -- a former star Notre Dame defensive lineman -- was shot in the chest in a horrifying incident in Florida ... but thankfully, he says he's doing alright now.

Cops in Jacksonville, FL say they responded to a gunfire call at around 9 PM Tuesday at a local gas station ... and found Nix lying wounded on the ground.

Officers say emergency medical personnel immediately rushed Nix to the hospital ... and there, a doctor told them Nix had said he appeared to be the victim of an attempted robbery.

In the police report, obtained by TMZ Sports, cops say doctors told them Nix said, "the suspects put a flashlight into his face" and said something along the lines of "give me..." to him.

Officers say doctors told them Nix felt a gunshot to the chest when he pushed one of the suspects away.