You only received one payment, even though you received two reporting forms, right? One form, the correct one, the 1099MISC, you reported as rent. This will be the money you return to your tenant.
The other 1099-NEC is for money you have already reported. It is incorrect. You will add it as other income and then back it out with the explanation of "double rent income incorrectly reported on Form 1099-NEC". You make a second entry with a negative amount to zero this out. This way, the IRS sees you reporting the 1099-NEC, but you are not taxed on it.
