You are most likely fine. The fact that you blew your lid and now have a steady bubble is a great sign of a strong fermentation. Even though the lid came off and the beer was "exposed", at that point it was cranking out so much C02 that there was very little chance of anything getting in to contaminate the beer. I've had the same thing happen to me and I would bet 90% of the brewers on here have as well.
I'm hoping you wiped everything down with a clean sanitized cloth and re-sanitized your air-lock before you put it back in. If you didn't, then just know that for next time. But either way, you should definitely not pitch this to start over. It is most likely fine.
Good luck and hang in there. The first batch is nerve wracking Try to relax and enjoy the process. I'm sure you made some great beer.