Hi, I Fell On My Back And Hit My Backside

Hi, I fell on my back and hit my backside two weeks back, the first two day I had pain but then it went off. However, now there is a tingling feeling from my back down to my feet, it is not painful but it is disturbing. I also found a very tiny lump on my back just a couple of days ago and not sure whether this is caused by the fall. Please advise.