Alright, probably nothing, but I figured I'd ask all of you here since i'm an idiot, and you guys aren't.....

I went to toss gas into my tank... and when I unscrewed the gas cap, it made a pressurized sound like opening a bottle of soda.... is this a bad thing?

What would make it do that? If it IS a bad thing, how do I fix it?

Thanks for your help!