sickofstupidity

I have had no problems moving the shifter from Park to Drive until yesterday. When I push the button in with my thumb it does not seem to push the locking/unlocking mechanism far enough down for me to move it out of Park. I have to get my finger or a flat head screwdriver in the opening and push the lock down. Once I get it out of Park the gear shift moves smoothly throughout Drive, Neutral and Reverse. What is causing this and what should I do? Trying to save money, hoping that this is a simple fix.