Dell B130 White password screen

So my roomate is being a dick and he messed with my laptop while i was at work. now when i turn it on, the black screen with “dell” on it comes up and the bar loads, then it goes to a white screen saying “this computer system,….., is protected by a password authentication system….Please type in the system administrator password. He’s a tech guy and im not so much. Is there anything i can do to get rid of this screen short of having a scuffle with this guy. i got homework n stuff to do and need my computer. Its a Dell B130. anyone that can help, please do. Thanks
-Trever