What's the name of a finger warhead?

Playing with your fingers is called playing with your head.

Tap your finger lightly on your forehead or someone else's forehead, and your head will rise backwards, making the tapping part bounce. This activity is called "bouncing the forehead". This is an entertaining action, which is common among friends or while playing. Besides "bomb amount", there are other similar terms such as "bomb amount" and "bomb amount".