I fell down and hit my chin two weeks ago.  There was severe bruising which is totally gone, but now there is a small hard lump under the surface of the skin on my jawbone.  When you touch the lump, it is tender but not too painful.  I am healthy, 40 years old, and have had no prior trauma to the area.
Hi. Thanks for your query... This looks to be a small remaining part of hematoma going into a stage of organization. This will resolve but take more time, so nothing to worry about. More important is to see that the TM joints are normal. Get checked by opening the mouth widely and close. If there is no problem in front of the ears, you are lucky, as these type of injuries cause trauma to the joints. You need no active treatment, although you may take anti-inflammatory for a few days to see if the swelling is reducing better, you can continue till the lump is resolved.