Yes you should have malpractice insurance. It the same as having fire insurance if you buy a house. You need fire insurance, yes you may, will probably, live your whole life and never need it. If you do ever need it you will be very glad it is there.
Your employer may have some general kind of malpractice insurance coverage for its nurses. However if you run into a "problem" the first thing your hospitals insurance company will do is try to find a way you did not exactly follow hospital policy and not cover you. You will need your own insurance.
There are a bunch of older threads here with extended discussion of the pros and supposed cons of carrying your own coverage, if you're interested. I'm sure you could find them easily using the "search" feature.
IMHO any nurse who is not carrying their own malpractice insurance is a fool or has nothing to lose if sued. I have adult responsibilities and two homes that I stand to lose if I am successfully sued. I have carried my own 2 million dollar policy since nursing school. Because I've had it so long the premium is reasonable and I don't worry so much.
You may wish to check out several of the threads authored by Risk Manager about malpractice insurance. Usually starts a good discussion. There's also several other threads by others. You should easily find them by searching for malpractice insurance as your keywords.