Hi Myagerreff,
If the branch is actually broken away from the main stem, I don't know if there's a way for it to heal but you can lop that branch off, let it sit out for about 24 to 48 hours to callous over and then plant it; it will form roots and you will have a new tree!
We have a Plumeria forum here on garden.org that you might be interested in, with many members who grow and love those beauties:
http://garden.org/forums/view/...