First days are always horrible!
Not just for you but for everyone. To be nervous and make mistakes is normal, dont´be worry about that .
I can give you a piece of advice that works wiht me.
take some pills to be cool, do some kind of meditation or just relax your self and fill you up with nice thinks as "everything its going to be ok" "Im´good in my work" "i dont need to be perfect because Im´just a human person and its normal make mistakes""Im´always giving my best so I can be proud of my self, "....well you know, all that kind of thinks witch make you feell better and more confident.
Look yourself in the mirrow and say " Im´cool, i love my self ....bla.bla..."
I konw it sounds a bit silly but can work, belive me.
And at work smile as much as you can (becareful , you dont need to look like a fool),but, you konw, people like smile.
50% of the people are cool and they will understand you are nervous and you are shy because everyone is different.
Dont pay attention to the rest, they are just assholes and so simple than they cannot understand anything further than their own noses.
You dont need them. Fuck up all of them.
Love your self because that is essentially the solution for our problem
Good luck Annamaria