There can be two interpretations possible here.
The point of the second verse is to say each person is responsible for his own actions, and that is the same as what the first verse says as well. This is the interpretation of your translator.
Allah commands the Prophet to say: ⟪If I should err⟫ in what I am doing, ⟪I would only err against myself⟫ i.e. the punishment for the error is mine to bear.
If other people follow him and he erred and it was clear, they would bear the punishment for following him. They will not bear the punishment for the Prophet erring.
And this is a repetition of other more general verses in the Quran like: ⟪Those who have gone astray will not harm you when you have been guided.⟫ (5:105), ⟪whoever is guided is only guided for [the benefit of] his soul, and whoever goes astray only goes astray [in violation] against it⟫ (10:108), and ⟪Whoever is guided is only guided for [the benefit of] his soul. And whoever errs only errs against it. And no bearer of burdens will bear the burden of another.⟫ (17:15).
In all the above verses, someone could come and argue about the followers of someone who errs. But, the point is that those followers are responsible for their own actions and the leader is responsible for his own actions. Neither bears the burden of the other in the sense that anyone is affected by the other's deeds in the hereafter.
But, that doesn't stop worldly influence between them and it doesn't stop that the leader bears the burdens of his followers without reducing from their burdens. He bears those burdens because they are essentially part of his fault, not because he bears the burdens of another person's actions.
Allah says: ⟪That they may bear their own burdens in full on the Day of Resurrection and some of the burdens of those whom they misguide without knowledge.⟫ (16:25)
This is similar to the famous phrase "If I am right, it is from Allah. If I made a mistake, it is from me and from Shaitan."
So, the verse is saying: If I err, it is only me who erred against myself. If I get guided, it is from the revelations of Allah.
And Allah knows best.