Arjuna has just seen the universal form. Galaxies, fire, time itself. And the first thing he does when he can speak again is apologise.
At 11.41 he remembers how he used to talk to Kṛṣṇa: O Kṛṣṇa, O Yādava, O friend. Casually, carelessly, out of love. At 11.42 he asks forgiveness for every joke, made while playing, resting, sitting or eating, alone or in company.
At 11.44 he asks to be borne with as a father bears with a son, as a friend with a friend.
He has seen the infinite. What he grieves for is the friendship he took for granted.
The verses
BHAGAVAD GĪTĀ · 11.41सखेति मत्वा प्रसभं यदुक्तं
हे कृष्ण हे यादव हे सखेति।
अजानता महिमानं तवेदं
मया प्रमादात्प्रणयेन वापि।।
sakheti matvā prasabhaṁ yad uktaṁ
he kṛṣṇa he yādava he sakheti
ajānatā mahimānaṁ tavedaṁ
mayā pramādāt praṇayena vāpi
Unaware of Your majesty, and either out of negligence or love, or considering You to be a friend, whatever I have said rudely, such as 'O Krsna, O Yadava, O Comrade,'
BHAGAVAD GĪTĀ · 11.44तस्मात्प्रणम्य प्रणिधाय कायं
प्रसादये त्वामहमीशमीड्यम्।
पितेव पुत्रस्य सखेव सख्युः
प्रियः प्रियायार्हसि देव सोढुम्।।
tasmāt praṇamya praṇidhāya kāyaṁ
prasādaye tvām aham īśam īḍyam
piteva putrasya sakheva sakhyuḥ
priyaḥ priyāyārhasi deva soḍhum
Therefore, bowing down and prostrating my body, I implore Your mercy, O adorable Lord. As a father listens to his son or a friend to his friend, it is fitting, O Lord, that You, who are dear to me, should bear with me who am dear to You.
Going deeper
After the vision, Arjuna speaks as a friend. 11.40 ends his salutations from all sides. 11.41 then looks back: unaware of Kṛṣṇa's greatness, whether from carelessness or love, thinking of him as a friend, he has said things like O Kṛṣṇa, O Yādava, O comrade, too boldly. 11.42 asks forgiveness for any disrespect shown in jest, while playing, resting, sitting or eating, alone or in company. 11.43 says there is none equal to him in the three worlds. At 11.44 he bows, asks for mercy, and asks to be borne with as a father bears with a son and a friend with a friend. 11.45 turns to his delight and awe. The passage is in chapter 11, and what the Gītā says about love gathers related verses.