I have a rock hard lump that feels attached to my bone on my shin. no injury. what could this be?

Depends: It depends on where the lump is. If it is near the top of your shin along the midline where the patellar tendon inserts on the tibia, (go ahead and Google this) it is probably Osgood Schlatter and nothing to worry about. If it is in another location, you should see your family doctor or an orthopedist to order a set of X-rays that can evaluate the lump.