After hematoma (liposuction) my chest feels hard. Is that normal?

 A hematoma after liposuction is rare. It's always a good idea to evacuate a significant hematoma but even then there will be prolong convalescence including swelling which would explain the firmness of your chest wall.

The short answer to your questions is "yes", this is normal.  When blood gets out into fatty tissue and then the blood is evacuated, it's impossible to evacuate all the blood.  The residual blood plus some injured fat cells lead to an inflammatory process whereby white blood cells come to clean up the free heme and fat.  This active inflammatory process will feel very rigid for a month or two, and then resolve.  If you were my patient, I would recommend ultrasound (the kind physical therapists use for sore muscles).  This will hasten the resolution of the inflammatory process and therefore get rid of the hardness.