I have a question about Unwraping?

As you can see on the right side,
I’m painting the cube…
and the color blue is smudged
to the left and right.


Is there a way I can lock the squares on the right side,
so that if I paint one square, I cannot paint the other squares
because I am locked on one square?

I hope this isn’t confusing.

Select the faces you only want to paint on, then in texture paint mode press the button on the header. This will only then paint on that face when texture painting in the 3d view not in the image editor window