Jimmy Fallon -- My Finger Almost Got Amputated (VIDEO)

Jimmy Fallon almost had a finger amputated and spent 10 days in ICU ... and it was all over his wedding ring.

Fallon talked about the freak accident on "The Tonight Show" Monday ... his first appearance since the injury.

TMZ broke the story ... Fallon was rushed to the hospital June 26 after a severe injury at his home.

Fallon describes how he tried to break a fall in his kitchen and his ring got caught on the counter, almost ripping his finger off.

Gnarly.