I googled "forehead jewelry" and found a lot of them in google photos, but I'm looking a specific name for this type of jewelry that falls on the forehead (and couldn't find there one).
I'm not aware of any generic English term for this type of jewelry. Such jewelry is not a common element of any English-speaking culture's fashion.
The items in your photos appear to be maang tika, but this is not an English name and chances are not a name that most English speakers will be familiar with.
As the other answers suggest, you can use the common Indian names for these jewelry -- but you might have to describe them for those who don't know what you mean. You could call these a kind of "jeweled headband", although "tiara" might also work:
tiara (n): A jeweled ornamental band worn on the front of a woman's hair.
Most "tiaras" look very different from these Indian styles, as they are more like crowns, and very ornate:
A "tiara" can have a simple design, such as those worn by brides:
There is no distinct line between "headband" and "tiara", for example this item marketed as an "amethyst tiara / simple amethyst headband":
As you might expect, "tiara" sounds much fancier than "headband".
(Edit) I found many hundreds of items from a google search on "forehead tiara". Here are seven images from this very long list: