The Krsna known as Yadu-kumara is Vasudeva Krsna. He is different from the Krsna who is the son of Nanda. Yadu-kumara Krsna manifests His pastimes in the cities of Mathura and Dvaraka, but Krsna the son of Nanda never at any time leaves Vrndavana

Expressions researched:
"“‘The Kṛṣṇa known as Yadu-kumāra is Vāsudeva Kṛṣṇa. He is different from the Kṛṣṇa who is the son of Nanda Mahārāja. Yadu-kumāra Kṛṣṇa manifests His pastimes in the cities of Mathurā and Dvārakā, but Kṛṣṇa the son of Nanda Mahārāja never at any time leaves Vṛndāvana.’”"

Sri Caitanya-caritamrta

CC Antya-lila

The Kṛṣṇa known as Yadu-kumāra is Vāsudeva Kṛṣṇa. He is different from the Kṛṣṇa who is the son of Nanda Mahārāja. Yadu-kumāra Kṛṣṇa manifests His pastimes in the cities of Mathurā and Dvārakā, but Kṛṣṇa the son of Nanda Mahārāja never at any time leaves Vṛndāvana.

CC Antya 1.67, Translation and Purport

“‘The Kṛṣṇa known as Yadu-kumāra is Vāsudeva Kṛṣṇa. He is different from the Kṛṣṇa who is the son of Nanda Mahārāja. Yadu-kumāra Kṛṣṇa manifests His pastimes in the cities of Mathurā and Dvārakā, but Kṛṣṇa the son of Nanda Mahārāja never at any time leaves Vṛndāvana.’”

PURPORT

This verse is included in the Laghu-bhāgavatāmṛta (1.5.461), by Śrīla Rūpa Gosvāmī.