Pat steak dry and season with salt and pepper. Add 1 tablespoon of canola oil in the skillet on medium-high heat. Sear the steak in the skillet until medium rare, about 3 minutes on each side. Take the steak out of the skillet and slice. Add the diced vegetables to the skillet and saute until slightly tender. Reduce heat and add steak back to skillet. Put half a cup of fajita mix into each tortilla and sprinkle with cheese and sour cream.