Lindsay Lohan could be headed back to court sooner than she expected.  Apparently, Paris Hilton's brother, Barron, is planning the visit.

TMZ broke a story Friday involving Hilton and Lohan.  Barron told cops Ray Lemoine beat him up at Lohan's request.  And now he is planning to sue both Lindsey and Ray.

Sources close to the Hilton family say Paris met up with a lawyer Saturday afternoon.  That was right before she went on Instagram and threatened Lindsay.  Paris' message -- WATCH YOUR BACK.

Barron Hilton posted a picture of his face after he made his way to the hospital.  Paris commented on the pic,

"They both will pay for what they did. No one f***s with my family and gets away with it!!"

Meanwhile, Ray claims Lindsay is 100 percent innocent.  He says he only punched Barron because he got physical first and was sticking up for himself.