Windows 7: Help administration (windows 7 professional) issue

Hi guys I'm new to the forum.
Anyways, First of all, there's two computers in my house. Right now, I'm using my laptop which is fine. But, my other computer, upstairs has the problem. My step dad recently changed the computer, and now we have a more upgraded computer. It's a refurbished computer, so other people fixed it for him, even put the password on it and ext. They are close friends of his. So, he calls them for the password and they give it to him. Now, it's working great, and all of that. I see that the only user account is his user account, "Jesus" so I think, well I don't want to use his, I want my own. I go into his user account, I go to user accounts, and make a new user account, called "It's Titi niggie." Lol, I Know very stupid. Anyways, I change his user account which was ADMINISTRATOR to STANDARD USER, and change MINES to ADMINISTRATOR. By now, I'm thinking it's no big deal, because when I go back to the main screen, my new account will be there... ext. That was NOT THE CASE AT ALL. I go back to main screen, and the new user account I made was not there. So I'm like.... Okay I must have not saved it. I go to his account, type in his password, and it said this: "SORRY BUT WE CANNOT LOGIN BECAUSE THIS USER IS NOT ADMINISTRATOR. EXT EXT..." So, now I'm basically screwed. I can't log in at all, and it was all because of my stupid mistake. I thought my user account, being administrator, would replace his, but now I'm in such a big mess. Since I changed his to standard user, I guess it's not letting me log in. I really need your help. When he comes home, he will be pissed off. It's my fault.
I don't know what to do, I don't see any possible options.

This would only happen to me.
Please guys, help me :3