Canker sores, which are not serious but are painful, open ulcers that often develop on the gums, are another common cause of gum pain. Canker sores are small, shallow lesions that develop on the soft tissues in the mouth and gums. Gum pain can occur as the result of vitamin C deficiency. Scurvy (vitamin C deficiency) causes gums to become soft, tender, spongy and painful. Individuals with scurvy may lose some or all of their teeth.