There is a swelling on one side inside the nasal cavity without pain, which may be nasal polyps, nasopharyngeal fibroangiomas, nasal papillomas, nasal vestibular cysts and so on. 1. Nasal polyps: Nasal polyps can be formed on one side of the sinuses or the mucosa of the nasal cavity. If the size of nasal polyps is small, they usually do not cause any symptoms. 2. Nasopharyngeal fibrous hemangioma: It is mainly composed of two parts: proliferated blood vessels and fibrous connective tissue, and is usually not accompanied by pain. 3. Nasopharyngeal papilloma: it can be manifested as nasal congestion and intranasal mass, mostly on one side, usually not accompanied by pain. 4. Nasal vestibular cysts: usually manifested as a clear boundary of the mass, with a complete peritoneum, often found only on one side of the nasal cavity with a mass, may not be accompanied by pain. Inside the nasal cavity, there is a side of the swelling, no pain, go to the hospital in a timely manner, to clarify the cause of the disease, under the guidance of the doctor for standardized treatment.