Clicking noise when key is turned to the on position?

I recently got my oil changed about a month ago, and then about a week after, my check engine light came on. I thought it was because of my recent oil change and that it would go away but it didn't so yesterday, I took it to AutoZone for the engine reader and they said the reader says it has to do with the catalytic converter. I came home and later that night, tried to start my car and it would just click. I tried a couple more times and on the last time, the dashboard lights started flashing and it would not start anymore. This morning I gave it a jump and it started but I noticed now that when I turn the key to the on position but don't actually start the car, there's a noise that clicks 3 times. It stops and I turn the car on with no problem but I'm wondering if the clicking noise is something else, I have to worry about as well.