Progress Bar on startup, iPhone 4?

I dropped my iPhone 4 really hard months ago and now, every time i restart the iPhone, it doesn't respond, like the Lock Screen frozes and others too. So I have to force shut down the iPhone many times. But this time, it doesn't stop freezing and one time I've forced shut down it and restart it. On Start up, there's a progress bar below the Apple logo. I was so afraid if it's some kind of Reset, Formatt or something. I've turned it off for now and when i try again the progress bar is still there. Do you guys know what the iPhone is doing? Will it effect my data inside? And how do fix it?

Its reinstalling your OS, this happens when you first turn on older iphones, or when you jailbreak most new ones. It should be just the way you left it when it turns back on and if not it shouldn't be hard to install a backup from your computer.