Hi. I Fell Down My Porch Steps And Hit My

Hi. I fell down my porch steps and hit my lower back on the previous step really hard. I have a long, thick purple and red bruise. It hurts on the outside but not internally. Tonight I noticed that it looks like I have a tail on the bottom of my bruise. It was not there this morning. Would it have taken 24 hours for part of the bruise to show up? Should I be concerned?