I just had my moroe pierced and the piercer put in a 14g can i put in a 16g and be fine also he only gave me the stud i have in and not an extra longer or shorter stud and its swelling a lot?

The stud the piercer put in it should be long enough to allow for swelling.

Also, if you put a 16g (which is smaller than a 14g) in it, then the hole itself may become smaller but with some work can be stretched back out to a 14g or larger.