For low-cost dent repair to your car, try dry ice. Park your car with the dent in the sun and let the dent and surrounding sheet metal warm up. Then, wearing protective gloves, put a small block of dry ice over the dent. The rapid chilling of the metal will "pop" the dent without scratching the paint. Do not touch either the dry ice or the extremely cold body of the car with bare skin.
If there is a crease in the bottom of the dent, or a body support member under it, complete dent repair with dry ice may not be possible. Make sure to follow all dry ice safe handling precautions.