Though a stud is a more popular piece of jewellery for a nose piercing, a ring is more comfortable for many people, and you don't have to worry about the end of your stud protruding from your nostril. Nose rings are available in nearly any gauge, so they can be as bold or subdued as you would like. Your nose ring should be the same size as your piercing, though, if you want to insert it yourself. If you want to stretch your nose piercing, it's best to seek the help of a professional.
Prepare a clean workspace by first washing your hands, then cleaning a hard, flat surface. A tray works well, since your jewellery can't easily roll off of a tray. Dry it, and then put a new paper towel over the area.
Clean your nose ring hoop as well as you can by washing it with antibacterial soap, if it isn't sterilised. It's best, though, if you have a piercing studio sterilise any new jewellery in an autoclave. An autoclave is the only way to ensure a nose ring's sterility.
Drop your clean jewellery onto the workspace. If it's sterilised, you shouldn't touch it.
Wash your hands again, as well as your piercing. If you currently have jewellery in your nose piercing, wash the piercing with the jewellery still in it, then remove the jewellery.
Remove the ball from your nose ring hoop by pulling the ring apart gently, holding it over your workspace. Be prepared for the ball to drop out.
Place a small amount of antibacterial soap on the end of the ring to make insertion easier. Press the area next to the piercing with a finger, then insert the ring into the hole.
Push the ring gently through the hole and turn it so the opening of the ring is pointing down. Push the ball into place. You may need to press the ring together with your fingers to close it enough to hold the ball.
Use a hot compress against the piercing if you can't insert the ring easily. If that doesn't help, go to a professional to get the new ring inserted.
Don't force the nose ring into your piercing. Doing so can cause the piercing to tear and can lead to infection.