Hi there, Thanks for your query. A blunt injury in the stomach might have caused a slight bleeding in the stomach/intestine. Or, the bleeding may have been due to a pain-killer, such as, NSAIDs, which you might have taken for punch-induced pain or for headache. The abdominal distension too may be due to transient shock of the intestine following the blunt injury. Do NOT take pain-killer now. Instead, take proton Pump Inhibitor such as Omeprazole or Rabeprazole twice daily till your abdominal pain is gone. Consult your doctor and apprise him of my opinion. I am certain that he agree with me; order required tests (if indicated), and- based on the reports- will prescribe suitable treatment as advised. If you find my response helpful and informative, do not forget an “excellent” rating to my answer, to encourage all doctors- engaged in social service- to render sound advice to the FREE queries. Lastly, if you need a detailed and prompt answer, you may post a Direct Query (Premium) addressed personally to me. Fond regards and have a nice day Dr. Rakesh Karanwal