I'm going to guess that one of the following happened:
1. You still have a short in your outlet so you can't reset the breaker. Locate and fix the short and you can reset the breaker.
2. Your breaker's spring has worn out and you need to replace it.
You can test #1 fairly easily with an ohmmeter, if you find zero resistance someplace you have a short you have to fix. If there is no short, you'll probably have to replace the breaker.
Oh, and Extrasolar is right, you should turn off the supply before doing electrical work.