Assuming the branch still has a connection not totally removed from the plant or that it has not dried out to much… Try adding damp moss to the damaged area of the wound , place both ends of the chewed off section together touching tightly be sure to cut ends even and match up both sides tightly together to mend. Then wrap the wound and damp moss with plastic and secure tightly with tape . Neither side cannot move , top or bottom section. This is a technique used to keep the area moist . Never let it dry out for initial mending of the broken area to take place and it must be carefully monitored.
Keep it damp not soggy use a eye dropper to add water. Keep in indirect light , a well heated area, and water the plant normally . Within 2-3 weeks peal back the plastic gently open the moss and check the repaired area. Usually the top section will still be green which means that the repair has been successful. This technique would help the plant heel itself . This needs to stay in place until the branch is completely repaired up to two months or more. I have used this technique on many small shrubs and small trees as well as many soft branched type houseplants.
If repair is not successful look to see if there are roots growing from the repair inside the moss. In this case the ends were not secured tightly or trimmed to match the cambium layers and structures. The roots will continue grow under the conditions and you could have a second plant . When roots have grown enough to support the newly rooted plant , then cut the branch free and you will have another rooted plant to grow from the mother plant. This is a form of air rooting or mending depending on how well the outer and inner structures of the cambium layers lined up correctly then it will mend if not you will have a second plant . At any case it is risky business . Good Luck.
