The boll worm which covers the opening once it enters into the boll is

The bollworm which covers the opening once it enters into the boll is Pink boll worm.
The pink bollworm is an insect known for being a pest in cotton farming. The adult is a small, thin, gray moth with fringed wings. The larva is a dull white caterpillar with eight pairs of legs with conspicuous pink banding along its dorsum. The larva reaches one half inch in length.
Since cotton is used for both fiber and seed oil, the damage is twofold. Their disruption of the protective tissue around the boll is a portal of entry for other insects and fungi.