Hello,
Heavy weight lifting followed by
bruise on skin of stomach is most likely to be due to
muscle strain with sometimes rupture of few small blood capillaries in skin giving way to cause bruising. (Blood vessels weakened by age or blood pressure are prone to get it or blood thinners can cause it which were not mentioned in the query.) There can be mild tenderness due to muscle strain.
Hernia is a condition where muscles of abdominal wall are weak and separate to give way and
peritoneal cavity and abdominal contents bulge out. There are no signs of bruising here. The bulge can be many times reduced (placed back in abdomen,
irreducible hernia causes lot of pain and tenderness).
The person under consideration does not have a bulge, but just a bruise more likely to be
stress to the abdominal muscles. Still he needs to be consulted for checking blood pressure/
anemia.
Ice pack for 15 to 20 minutes and few pills of
Ibuprofen should solve his problem (in case he does not have any of the problems mentioned above). A bit of raising of bed side for few hours would prevent pooling of blood.
Hope I have answered your query. Let me know if I can assist you further.
Regards,
Dr. Vasudha Jayant Athavale