You can try rearranging the furniture to cover up that spot on the rug, but you'd have better luck trying to get the stain out first. If it's just a little spill, water and a cloth might take it out, but for tougher stains, such as red wine or pet urine, you'll need a tougher solution. You don't have to look far; the solution is right in your shower!
A good spot cleaner for carpet stains is shaving cream. Take an old shaving brush or purchase a small, cheap paintbrush (that you keep just for this purpose) and use it to work the shaving cream into the stain. Then use a clean, damp rag to wipe up the shaving cream and the remnants of the stain. Blot the area dry with a clean, white or color-fast cloth.