Well, probably not the way it should have went down, but it's over and time to move on. Don't feel guilty or coddle the Pom about it. That will only make things worse.
The first thing I would do is make sure that everyone has a place to go to get away. If it is a crate or room or corner of the living room behind a chair, it doesn't matter. They have to have space if they need it. Enforce this so they both understand that you will step in if the offender is intruding.
I would crate one or both of them when unsupervised for safety.
From your description, I bet the Pom is willing to leave the GSD alone now. There isn't much you probably need to do in that department. Because your GSD was willing to take so much in the first place before reacting, you should use this experience to head off any negative interactions from now on. Protect the little dog and don't allow it to push the GSD over the edge again. You now know what is going to happen if you stand back and observe.
I would put some drag lines on the dogs when they are interacting so you can manage the situation from afar by limiting interaction through physical restraint. They may get along great after this, and they may have to be crated and rotated forever. It's up to you to observe interactions and intervene before anybody gets out of hand.
I would allow them to interact under supervision to see how the relationship has changed and go from there. Post back with an update to let us know how it's working out. If the little dog shows interest in approaching the GSD, I would allow it under close, calm supervision, and I would be ready to reel the Pom out if things look negative.