LL Cool J -- Back to Work After PUMMELING Home Invader

Two weeks after he beat the living daylights out of an alleged bad guy in his home, LL Cool J triumphantly returned to work yesterday ... where he beat the living daylights out of a fake bad guy on the set of "NCIS Los Angeles."

It's the first time we've seen LL since the incident ... and of course, the rapper/actor didn't have a scratch on his body ... unlike the home invader, who suffered a broken nose and jaw when he messed with the wrong house on August 22.

We tried to ask LL about the situation as he was walking to the Santa Monica set of his CBS show yesterday, but he was too "in the zone" with his scene to answer questions.

He did, however, flash us the fist pump ... to remind everyone that LL Cool J will break your face if you mess with his family.