First, blot up what you can with paper towels. Mix one teaspoon mild dish-washing detergent in one cup warm water, dip a clean towel in the liquid and, working from outside in, dab at stain.
Do not overwet. Rinse with fresh water and blot dry. Next, add on-third cup white vinegar with two-thirds cup water and dab on stain. Rinse with water; ;blot until dry.
Once area is totally dry (after at least 24 hours), sprinkle entire carpet with baking soda or rug deodoriser. Vacuum after a few hours.