If the gas odor is minor, not intoxicating, one of your pilot lights most likely needs to be re-lit. There are typically three pilot lights, 2 for the stove burners, and 1 below the oven. If your pilot light does not stay lit, try to wipe the any residue off the pilot light before re-lighting it. If this does not work submit a maintenance request.
If the odor is a strong sulfur smell that is so strong it is hard to breathe, leave the building immediately and call 911. You can also contact Xcel Energy at 800-895-2999.