1994 Chevy Caprice coolant temp sensor/check engine light

Ok I have a 1994 chevy caprice 173,000 miles on it my car runs like a champ the other day I noticed my check engine like popped on and I was cocern because I take good care of my car so I immediatly took it to pep boys and had it scanned a code 15 was the code it read which was a coolant temp sensor. And every since this my car doesn't start right away. So the next day I popped my hood and noticed the plug to the coolant temp sensor was daggling and I plugged it back up started the car check engine light went off and car fired right up so I knew that was really the problem. Now the thing is I still need a new sensor because the clip is broke on the sensor and won't stay plugged in so I bought a new sensor put it in and my check engine light came back on and my car won't start on the dime like it does. What could this problem be do I need to drive my car for awhile until in registers in the computer because I even installed the old sensor and everything works good. Or do I have to get the code cleared or what help me out please thanks.