स्वयमेवात्मनाऽत्मानं वेत्थ त्वं पुरुषोत्तम। भूतभावन भूतेश देवदेव जगत्पते ॥

swayam evātmanātmānaṁ vettha tvaṁ puruṣhottama bhūta-bhāvana bhūteśha deva-deva jagat-pate

Thyself indeed knowest Thyself by Thyself, O Purushottama; Source of beings, Lord of beings, Shining One of Shining Ones, Ruler of the world!

In plain words: Arjuna says that only Krishna truly knows Himself. He calls Krishna the Supreme Person (Purushottama), the source and ruler of all beings, God of the gods, and Lord of the world.