Red light, green left arrow?

The green arrow pointing left indicated that you were clear to take a left turn . . . Now if the car in front of you is not turning you can't just pull out and go around them.

My guess is you were in a lane that had the option of going straight or left and the driver in front of you wanted to go straight. In that case you need to wait for them to go before you can think of going . . .

But that is a guess without seeing the actual configuration of the intersection and what your local laws are. If you are in the UK it would be different than the US due to driving on different sides of the road. . .

If you are taking a left, you certainly can and should go... obviously you can't crash into the person in front of you. But yes, a green arrow specifically is to allow the person in the left lane to take the left while all other lights are still red

Usually in that situation there will be at least 2 lanes going in your direction. Some for straight traffic and some for left turning traffic. The Red ball light is for straight traffic lanes and the green arrow is for the left turn lanes. There should be no driver ahead of you waiting for the red light because he should be in a different lane than you. If there is a car in the left turn lane stopped with a green arrow, you should honk to wake them up. You can't pass a car in your lane in that situation.

Don't move if there's a car in front of you no matter what color the light is.