I have issue with connecting I2C LCD and carbon dioxide sensor to Arduino nano.
Arduino nano have a SCL and a SDA pin. The problem comes when I try to connect both LCD and sensor to Arduino nano. Board haven't two SCL and SDA pins.
It doesn't need to. You can connect SCL of the Nano, the LCD and the sensor and the SDA of all three devices as well. Since the LCD and the sensor will have different I2C addresses, the Nano can address each one separately over the same pair of wires. That's the whole idea of I2C.