Well, considering that electricity is constantly running through it, it might generate a bit of heat and since it is cased in plastic, it insulates it a bit...
custom builds can get hot try it in another computer.
What exactly are you basing that on?
i tried plugging the usb stick into another computer, but it didnt detect it. but it works on my computer.
i jst dont understand why my usb gets really hot on my computer
See: "USB devices are powered, meaning there is an electric current running through them from the second they are plugged in to the second they are removed, unlike PS/2 where there's just a signal transmission. Because of this, they tend to get warm, and some do get rather hot."