Hi thanks for yourr question..
The electric current doesn't stay in body and secondly it cannot damage your heart afterward.what ever damage it can produce it produces,during that time when you become part of electric circuit.After effects of current are burns,which it produces ,luckely you didn't get any burns.You must be having pain and spasm in the arm due to damage to the cell produced by electric shock
,for which you can take pain killer like paracetamol
There is nothing to worry now.
Hope this answers your question.