Yes, you can file as married filing separately OR you can file a joint return with your spouse. Generally, filing jointly will give you a bigger refund or less taxes due. When you file separately, your tax rate is higher and you won't be able to certain deductions or credits that you may only qualify for if filing a joint return. It won't matter if you were single when you earned the income, as the IRS uses your marital status as of Decmeber 31 for that year's income return.
Here is more information on filing jointly versus separately:
https://ttlc.intuit.com/replies/3288477
