beat some niggas face on yo mommas ass
Seems to mean that you've done bad, when you hear this it is likely from the mouth of a very ghetto woman. Regardless of whether or not you can tell the gender of the creature, run. If you are within grabbing distance, Run faster.

They can smell fear.
Ghetto chick(?): "Im funna beat some niggas face on yo mommas ass!"

You: "I'm soooorrrryyy!" (crying)

Ghetto chick beats you down.