I accidentally deleted the text icon. In settings on my iPhone 12
How to restore icon accidentally deleted on iPhone 12
iPhone 12, iOS 14
I'm not sure if you mean that you deleted the Messages app icon or not but if that's what happened, you can go to the App Store and search for Messages and redownload it there. The same is true for any app you accidentally deleted or intended to delete and want to have back on your phone.
Hope that helps.