So everytime I start up my G, it says maintenance tire on the dash.
At first I thought the air pressure would be low or something but it wasn't.
Not sure if the dealer is open tomorrow and IDK what to do.

What does this mean?

 

The only sensor we have in regards to tires are for pressure. So if pressure is good then it wouldnt be for that.

What you are describing sounds like the typical reminder that is set to go off at certain mileage intervals to remind to have tires rotated. Check your wear bars at all four corners, if are flush to the rest of the tire get them replaced. If all bars are bleow the surface but the rears have significantly less wear than the fronts have them rotated. If you arent comfortable with doing this take them to a shop, but really simple to do, or find out how with little searching.