NBC, according to Colin, has diagnosed him with leprosy ... true, the network brass aren't doctors, but it's a fair assessment after the 'SNL' star had to leave the games because he was doing himself in with gashes, bites and infections.

Colin himself said he's been declared a "leper" by his own network. That typically means he needs to isolate to protect himself and others. Obviously a joke ... but still, we get the point.

He's now on the island of Malta ... although we would've thought he might have been banished to Molokai, Hawaii ... which used to be the site of a famous leper colony.

"I wasn’t ‘sent home’ from the Olympics. NBC simply looked at my foot, declared me legally a leper, and exiled me here, to the island of Malta," he said.

Jost suffered a nasty toe injury on the reef at Teahupo'o, Tahiti, while he was surfing during his down time. That led to a staph infection -- and an ant infestation in his wound -- followed by a nasty ear infection that kept him out of the water for the remainder of his trip.

Scarlett Johansson's hubby seems to be enjoying his time in the Mediterranean ...  he hit up a local casino where he blew "the hundreds of dollars I’ve earned as a surfing correspondent."

Colin said he fit right in on the island ... since Malta was the home of multiple bubonic plague outbreaks.

Colin didn't look back with remorse on his time in Tahiti. He thanked the locals for their warmth and hospitality ... and for "occasionally looking at [his] foot and and whispering ‘Chupacabra.'"