In Sorry, can I be forced to move out of my "safe zone"?
Yes. From a PDF version of the rules, you are required to move if a legal move is available:


  ... if at any time you can move, you must move, even if it's to your disadvantage.


and from the description of the Safety Zone, moving backward out of the zone is legal:


  ... however, a pawn may move backward out of its SAFETY ZONE and on subsequent turns move back into the ZONE as cards permit.


Note that trading places on an 11 is an exception to this - you may decline to switch places with another pawn if you like - but yes, in your situation, you must move a pawn out of your safety zone.