If it's just general nervousness about "the unknown," then it will pass in time. Give it a few weeks until you've established a new rhythm. We find comfort in familiarity, even if it's painful familiarity (life lesson for me!)
If you're nervous for other reasons, you need to consider each one separately and determine what will help. I'm in a very similar boat- just started a new job last Monday.
So, I had a 4-day-long panic attack last week while on a trip up to NY (not due to the company I now work for, so far everyone has been great - panic due to massive change all at once). I had a lot of time to read articles on this topic. Here are some good ones to read through. Much of these focus on the "nervous about ability" topic, but I believe you and I are more nervous about the giant change all at once:
Why We’re Hardwired To Be Anxious At A New Job
5 Ways to Boost Your Confidence in a New Job
The GQ Therapist: how to handle new-job anxiety | British GQ
What To Do If You Feel Anxious About Starting A New Job
Plus I have to give a shout out to @Revvv who has been extremely encouraging over the last year. Not trying to derail the thread, but my life has changed massively since this time last year when I felt like I was spiraling down a toilet. A lot of good people on here.
Great reads bud thanks this helps out a bunch, they are all good to read, thanks for the help bud.