<s>[INST] I am 70 years old I am on blood thinners earlier this morning I was getting out of my vehicle and the door came back and hit me on the elbow it is swollen about the size of a golf ball and it is purple and black what could be the cause should I see a doctor [/INST] Hi there In my opinion Purple and Black colors  indicate internal bleeding since you are on blood thinners , you will need aspirationalso there is the possibility of crack fractureuntill you see your doctor or get admitted to ER use ice packsGood Luck </s>