Assuming you did not pass the Substantial Presence Test for 2020, you are by default a nonresident alien for all of 2020. A nonresident alien cannot file jointly (unless treated as a resident). The only married option on the 1040-NR is Married Filing Separately.
However, if you were present in the US for the last month of 2020 and those days counted in your Substantial Presence Test, and you will pass the Substantial Presence Test for 2021, there is a way to make both you and your spouse resident aliens for all of 2020 and file jointly.
You first use the First-Year Choice, which would turn you into resident for the part of 2020 after you were present in the US for the purposes of the Substantial Presence Test. (In order to use this, you would have to wait until you pass the Substantial Presence Test for 2021. The exact date when you will pass depends on how many days of presence you have from 2020. You may have to request an extension of 2020 taxes in order to wait for this to happen.) This makes you a dual-status alien (nonresident at the beginning of the year and resident at the end). A dual status alien also cannot file jointly and cannot use the standard deduction.
Then, you would use the Nonresident Spouse Treated as Resident option, which would make both of you resident aliens for all of 2020, and force you guys to file jointly. You qualify to use this because you are married and (after using the First-Year Choice) one of you was a resident at the end of the year and the other was nonresident. (Note that as resident aliens, all of you guys's worldwide income for the whole year would be subject to US tax, although you may be able to use the Foreign Earned Income Exclusion and/or Foreign Tax Credit to reduce US tax on foreign income.)
If you are treated as resident and file jointly, you guys will have a $24,800 standard deduction (whereas as a nonresident alien you do not have any standard deduction).
Update: I see that in the comments you said you were only in the US for 15 days in 2020. So you would not qualify to use the First-Year Choice, and I think Married Filing Separately is your only option.
