A sore inside the nose can be caused by a common cold, a viral infection or nasal allergies, according to WebMD. An injury to the nose caused by a blow to the area or nose trimming can also cause sores inside the nostrils.
Individuals with allergies or sinus infections commonly experience sores inside the nose, explains WebMD. Irritation from a runny or stuffy nose can cause sores to form due to drainage that irritates the interior of the nose. People with colds or allergies should attempt home treatments such as nasal rinses, nasal spray or a decongestant to minimize drainage.