"A Christmas Story" star R.D. Robb knows ... NEVER triple dog dare anyone to lick a frozen pole -- and don't run people over with your car, allegedly, because they'll sue you.
TMZ has learned 40-year-old R.D. -- who played Schwartz, Ralphie's friend in the holiday classic -- is being sued in L.A. by a woman named Shelli Tollman.
In the docs, Tollman says she was walking across a street last March ... when R.D. came around the corner in his 2012 Mazda 6 sedan and hit her.
The suit doesn't mention specific injuries ... but Tollman does claim she suffered mental, physical and emotional pain as result of R.D.'s "negligence" and "carelessness."
Tollman's suing for unspecified damages.
Speaking of damages ...