hi wallace, looks like you have bruised yourself. A little soreness is to be expected and also it will turn purple as there is a blood clot formed there. It will stay sore for a few days and eventually the bruise will change colour from blue to green to yellow and fade away in a week to ten days. You need not take aspirin
if you do not have any pain. At present you may not visit a doctor either. If the pain increases or if you have any problem in movement of the joint then you may visit a doctor. A bruise should subside on its own in 7-10 days. Take care!