hi, thanks for your query.
The hard lump after trauma could be due fibrosis
as a part of healing process of the damaged internal tissues.
Reappearance of bruise
might be due to trivial trauma which you might have not noticed.Aspirin
can lead to easy bruising so it is not advisable.
you may consult a doctor so that it can be examined properly for exact diagnosis and appropriate treatment.
Hope this helps.