Gum in between teeth has small bright red streaks. Very painful whiteish spot under gum skin a bit below red streaks. Gum not bleeding when flossed.

Lesion. Any lesion must be examined to be diagnosed. Whether the lesion is on your toes, your elbow, or your gums, it must be visualized, palpated, explored, to be understood. Only with comprehensive diagnosis can treatment plan be properly formulated.
Infection or injury. When the gum tissue between the teeth (papilla) has these symptoms, it is usually a localized infection. This can result from an injury or trauma, a buildup of calculus (tarter), food impaction (a popcorn husk ?). It could also be an ulcer although they do not usually occur in this area. Clean thoroughly but gently, rinse with warm salt water, and do not irritate. Check with your dentist.
Aphthous stomatitis. Or canker sores the most common observable lesion by the dentists.The topical anesthetic otc application is recommended. Individual ulcers typically last 7-10 days.