Đảm bảo trang sức vừa vặn. Tuyệt đối không xỏ khuyên sụn bằng súng xỏ khuyên. Tránh va đập hoặc gõ vào lỗ xỏ khuyên.

Given the above summary, write a detailed text in English for it.
Loose jewelry can move around inside the piercing, disturbing the cartilage and causing a bump to form.  Therefore it's important to get jewelry that fits the piercing perfectly. A professional piercer from a reputable salon can help you with this. You should also avoid wearing earrings with butterfly backs, as these are more prone to causing bumps. Piercing guns should never be used for cartilage piercings. However, some cheaper or less-professional piercing places still use them.   Piercing guns jam the jewelry through the skin, which distorts the ear cartilage underneath and often causes bumps to form. Therefore, if you plan on getting a new piercing, avoid getting it done at a place that still uses piercing guns. Frequently bumping things off your piercing or getting it caught in hair or clothes causes the jewelry to move around and can lead to bumps.   Tie long hair back as much as possible (particularly when sleeping) to prevent it from snagging in the jewelry. And in general, just try to be more aware of your piercing and do your best to protect it. Don't fiddle with it or touch it constantly.