I don't have much experience in auto body repair, other than listening to what adjusters say when walking around cars I have owned that needed repair work. Some dents are fixable through paintless dent removal. Some need to be drilled and pulled. I'm not sure anything would look good if pounded on from the other side... I could be wrong, but I don't see how you could get a smooth surface using anything to pound it out from the inside.

I would take it to a dent removal shop and see what they think.