Lymphocystis is a viral disease, by my understanding. And it usually hits mouth, gills and fins. It's not really positioned for that, and it's far too large to be an Ich cyst. I'm stumped.
Ideally, let the angel go, Coral Beauty angels are rather hardy. If he starts behaving oddly, not eating, etc, isolate him, and since we can't figure out what it is exactly, administer formalin, and do what you can to get him eating.