LCD Doesn't work

Hi i'm new to this kind of stuff. I bought a LCD display with I2C connection and when i settled all I2C pins to the lcd it only showed the I2C power led on. Then i came back to solder again the 16 pins and now it appears that the ON led of the arduino shows low light and L led goes down. Did i broke it? And the power led of the I2C doesnt power anymore

Sounds like there is a short on the LCD pins.
I'm assuming that this is a PCF8574 based i2c backpack that you soldered to an hd44780 LCD?
Can you post some clear photos of your soldering?
Show both sides, the LCD backpack side as well as the other side where the backpack is soldered to the LCD module so we can see all 32 solder connections.

I would not recommend using it any more until we can take a look at it.

--- bill