Should I file in Nevada & California or just Nevada? I moved to California with my boyfriend for his law school. I have a job out here, but nothing else is attached

[MarilynG1]

If you earned income in California, you can file a Part-Year Resident Return there and report your California earnings and any California tax you paid.

Nevada has no Income Tax. 

Click the link for more info on How to Allocate Income for a Part Year Resident.

[Hal_Al]

You have to pay CA tax on the income you earned there. The question is do you file as a part year resident or non-resident.  The answer is not clear cut and depends on all the particulars. The general rule is that an out of state student is still a resident of his previous state until he changes it.   A student's spouse would generally be treated the same. Girl friend of the student, not so much.

Do you maintain a home in NV?  What is the anticipated length of your stay in CA? You most likely should file as a part year resident; which means all your income, received while a resident (Interest, dividends etc), as well as your wages are subject to CA tax.

See  https://www.ftb.ca.gov/file/personal/residency-status/part-year-and-nonresident.html