Bruce Jenner -- Nose Mystery Solved ... It's Skin Cancer

Bruce Jenner underwent surgery for skin cancer on his nose earlier this week ... TMZ has learned.

Our Kardashian-Jenner family sources tell us Bruce had a chunk of tissue removed from his nose on Monday ... and the procedure required 30 stitches.

Bruce was spotted with some serious bandages while getting his morning coffee Tuesday in Calabasas -- and everyone's been wondering what the deal is.

We're told doctors attribute the cancer to sun damage -- remember, Bruce plays a lot of golf.

Bruce underwent the same procedure back in 2012 -- that time the cancerous tissue was on the side of his face -- and docs warned him to use better protection.