My dashboard says my driver door is open

That sounds like the door ajar switch is starting to fail, or if the door moves a bit when you pull on it the latch may not be closing fully and moving the switch into the closed position. The switch is on the body at the back of the door opening. There are two parts of the switch. One turn on the interior light and the other turns the door ajar light on. Are the interior lights also on when the dash warning is? If not then I suspect the switch is starting to fail internally. If the lights are also coming on then it may be that your door latch or striker is worn and allowing the door to move away from the switch. Many times the striker can be adjusted to make the door close tighter. It looks like the image and has two screws that hold it. You may be able to loosen the screws (Do Not Remove Them) and gently tap the striker in towards the body just a small amount and then tighten them down again and get the switch to operate properly. Before you try that make a mark around the striker so that you can put it back into the original spot if moving it doesn't work.

If however only the door ajar light is coming on and not the interior lights you can try replacing the switch in the body. That is the second image. It has one screw and then comes out of the hole. I like to run a wire through the harness just to be sure the connector cannot go back into the car while you remove it from the old switch and attach it to the new ones. Even clipping a pen or similar to it will work to hold it.

Any shop should be able to adjust it as it's nothing but a couple of torx screws if it's just the striker. Price wise it will probably be the minimum charge as it might take 10 minutes to adjust it. If it's actually the latch that is the problem it will cost more as the door has to come apart. A test you can try would be to gently close the door, most latches have two catches in them. Sort of a built in safety. Close it slowly and see if the second catch works, then close it fully and see if it falls back open to the first catch or if it stays closed but is just loose. If it is falling back to the first catch it is more likely the latch. You could try lubing it with some silicone spray or similar. Then using a pen or screwdriver to work the latch closed and open to get the lube into the latch. Similar to this but you would spray the lube in then rock the latch with the screwdriver.
https://www.youtube.com/watch?v=wmWsM-TSaKo

If the latch frees up and now the light is out you fixed it.

The video was just showing a method to move the latch when you lubed it. If the latch is working and it is fully closing then it is either the striker is worn or the switch that is bad. A simply trick to see if it's the switch, tape a piece of cardboard to the door where it pushes the switch. Does the light and door ajar go out? If yes the switch is working but the door isn't closing far enough. If it doesn't then the switch is bad.