Yawning is not generally something you should see outside of shedding and shortly after a meal. It may be nothing, but it's at least something I would investigate. Could be a sign of RI. Depending on your level of experience, if may be worth having an experienced reptile vet check him out if you are not sure what to be looking for.

A week of not eating is nothing to be concerned with, frankly I wouldn't have even attempted to feed until 1 week mark of bringing an animal home. Is this a hatchling or an adult? What he was doing in someone else's care without information of the husbandry there may mean nothing too.