I had mine done a few years ago and found even after 6 weeks the hole was still trying to close up so if you do change to a smaller stud remember to twist it and take it out regularly otherwise it might get stuck there as they skin grows back! It probably stopped doing this after more like 10-12 weeks at a guess.
ive had mine done twice and they never truely heal. i got a sore lump both inside and outside my nose around the piercing so would say wait as long as you can and keep it really clean. dont go too small on the stud as it will close round it. ive had mine out for nearly five years and stil have a mark on the outside and a small lump on the inside which gets sore when you have a cold.