Electronic – Using a 5V LCD screen from a 3.3V Raspberry Pi GPIO pin

It's hard to tell from your description (well-focused, properly cropped, well-lit photos would help) but ...

The "black dots on the back" are probably "Chip on board" (COB) packaging of an LCD controller IC. If that's heating up to near 100C ("boiling), you certainly have problems and are at or beyond the point of permanent damage.

^{Photo©MikroLogika
Photo©RedGrittyBrick}

As I said in a comment, my best guess (and it's a guess because there is insufficient information for anyone to know the answer) is

• You haven't wired up your circuit correctly and/or
• The diagram you are following is incorrect and/or
• Your module isn't like the one in the tutorial you are following.

These type of LCD module come in 3.3V and 5V variants. The tutorial you are following is drawing power from the Pi's 5V pin and is for a 5V module. Maybe your LCD module is a 3.3V variant. In which case it should not be connected to the Pi's 5V power pin.

Note: "The maximum permitted current draw from the [Raspberry Pi's] 3.3 V pin is 50 mA."

If you look at a datasheet for an example 3.3V LCD module you'll see that it claims a supply current (I_DD) of 2.5 milliamps, the backlight current (I_LED) is 19 millamps (mA) So if you are measuring over 1000 mA (1 A) - something is very very wrong.

From RPi 3.3V to 5V input, depends on the input IC's Input Logic High minimum. Most ICs are 0.7 * VCC, or 3.5V. So the 3.3V won't be enough to register as a Logic High. Some ICs are 0.6 * VCC, or 3V. It will be enough, maybe. Sometimes it will act in weird ways at such a low voltage. You need a level translator circuit. A simple NPN transistor can do it, but inverts the logic (3.3V Output = 0V Input, 0V Output = 5V Input). You could fix that in code, or you need a more complex circuit or dedicated IC for non-inverting.

From 5V output to RPi 3.3V input, you always want to convert it, as the RPi does not have 5V tolerant inputs. NEVER connect it directly, even with a serial current limiting resistor, unless you want to buy a new RPi. A simple way could be a resistor voltage divider. A better way would be a real logic level translator circuit.