Hi Lei, You have developed a bruise or contusion due to your nasty fall. Bruise develops when due to trauma blood vessel gets injured and blood spills in surrounding tissues. To help in pain relief Take an analgesis like paracetamol or brufen. It will settle the pain and swelling Use ice compresses over the area one or twice in a day Use of of vitamin k and vitamin c helps in easy and early healing of bruise If with all these suggestions swelling persists, consult a doctor near by to rule out any bone or deep tissue injury. Hope that answers your query.