You must seek care from a dentist. Your issues cannot be treated at home, must be professionally done at a dentists office.
I Have One Tooth That Looks Like a Popcorn Kernel What is It and How Can I Treat It at Home? (photo)
Doctor Answers 2
Treating developmentally stained tooth
Popcorn Kernel Looking Tooth Cannot Be Treated at Home
The picture is fuzzy, but there appears to be a developmental defect in that tooth, perhaps caused by a high fever or injury when that tooth was developing years ago. There really is no home treatment for it. A dentist can cosmetically improve it.