Krsna was smiling because He was thinking to Himself - I have delivered two young demigods from the bondage of standing for a long time as trees, but as for Me, I am bound by the ropes of the gopis and am subject to their chastisements

Expressions researched:
"Kṛṣṇa was smiling because He was thinking to Himself" |"I have delivered them from the bondage of standing for a long time as trees, but as for Me, I am bound by the ropes of the gopīs and am subject to their chastisements"

Srimad-Bhagavatam

SB Canto 10.1 to 10.13

Kṛṣṇa was smiling because He was thinking to Himself, "These two young demigods fell from the higher planetary system to this planet, and I have delivered them from the bondage of standing for a long time as trees, but as for Me, I am bound by the ropes of the gopīs and am subject to their chastisements." In other words, Kṛṣṇa submits to being chastised and bound by the gopīs because of pure love and affection worthy of being praised by a devotee in so many ways.

SB 10.10.39, Translation and Purport

Śukadeva Gosvāmī continued: The two young demigods thus offered prayers to the Supreme Personality of Godhead. Although Śrī Kṛṣṇa, the Supreme Godhead, is the master of all and was certainly Gokuleśvara, the master of Gokula, He was bound to the wooden mortar by the ropes of the gopīs, and therefore, smiling widely, He spoke to the sons of Kuvera the following words.

Kṛṣṇa was smiling because He was thinking to Himself, "These two young demigods fell from the higher planetary system to this planet, and I have delivered them from the bondage of standing for a long time as trees, but as for Me, I am bound by the ropes of the gopīs and am subject to their chastisements." In other words, Kṛṣṇa submits to being chastised and bound by the gopīs because of pure love and affection worthy of being praised by a devotee in so many ways.