I am sorry to hear that you had a major fall that led to a keloid forming on your waist, and that the fact you developed a keloid in the past has you worried that if you get your nose pierced that you may develop a keloid on your nose. I am happy to give you some general information about scar formation, and what exactly a keloid is, but ultimately I am going to recommend that you make an appointment to be evaluated by a dermatologist
. They will be able to examine your skin, your scars (including the one on your waist), and take more of a history which I am unable to do in this setting. That is ultimately what you need to get the most accurate answer to your question. Often times people misuse the term keloid to describe other types of scar formation. For instance a scar that is larger than normal, and sticking out above your skin can be either a hypertrophic scar, or a keloid. the difference is that a hypertrophic scar is large, but respects the boundaries of the original injury
(meaning that if there was an incision, it does not extend beyond the incision site). A keloid is a hypertrophic scar that extends beyond the margins of the wound. Both involve too much deposition of collagen, and can potentially be mitigated with topical or injectable steroids. The dermatologist will be able to tell you for certain if what you have is in fact a keloid, and if so, how best to manage further injuries (like a piercing).