Bullying or dominance behaviour is quite natural. Only worry if it leads to blood being drawn. Normal bullying looks vicious to us, but piggies say things to each other with body language so bumping, shoving and generally being physically rough is quite normal.
Getting another piggie may result in more bullying not less. Your two piggies are trying to work out which of them is top piggie, which they will do in time. Another piggie put in then means you just have three piggies trying to work out which one is top piggie - you see what I mean!
Telling them off doesn't work. Look out for bites on face, shoulder or rump. Separate if those happen. Don't worry about squealing or nicks on ears. I do hope all the fuss settles down very soon.