What if I didn't sign out of my old Apple ID before I changed it and got a new one?!?!!?

So I decided to change my Apple ID, which I shouldn't have, on my laptop but I didn't sign out of my old one on my iPod Touch 5g so now it's causing problems!!!! I can't download apps!!! I also can't update apps!!!!! So could someone please help me please??!!? That would be great!!!!! This is very stressful!!!!