If Hepatitis A is the one on the arse, it's more uncomfortable than painful. I think typhoid, cholera and something else used to be combined in one injection and that could be f***ing painful for a couple of days and make the area injected come up like a balloon. Not sure they combine the three anymore but don't think they do and it's not too bad from memory.
Just checked and it seems hepatitis A and B are given in the arm. Now trying to rack my brains as to what I was being immunised for with the one I had on the arse