in your situation there is no requirement to file an amended return. so it your choice since an amended return carries a TT fee. you can wait to see how much the loss would save you on your 2019 return
The IRS will accept an amended return up to 3 years after the date you filed the original return. If you filed before the April deadline, the IRS considers the April deadline to be the filing date. if you extended your 2018 return the amended return due date is on or before 3 years the date the IRS received your return
