Thanks for the query to H.C.M. Forum.
When strike with a blunt object than there develops hematoma
( collection of blood ) underneath skin.
Same thing happened in your case.
As you stated that when hangs down ( hand ) , you feel pain means due to anti gravity.
Ice pack massage
, serratiopeptudase , aceclofenack will provide complete relief.
Rest and raise hand above body , support under soft pillow.
Within 3-5 days , you will be alright.