To be nervous is to be anxious about something, or anticipant. To be worried can also mean this, but usually it is used in more negative tones. To say that you are worried about something is to be anticipating negative outcomes, whereas to be nervous, you can be more than just anticipant of the worst - you can just be 'antsy' and jittery.
To say I am worried about my presentation means that I am scared it is going to go wrong. I am expecting a bad result because I did not prepare well for it, and I don't think I am going to perform well.
To say I am nervous for my presentation means that I am jittery, and I don't know how it going to go. I prepared for it, but I am getting butterflies in my stomach because I get nervous when I present. It can go very badly, but I can also do very well on it.
I don't know if this is enough of an explanation. Let me know if you want more context or examples please!