פּירוש אויף ויקרא 10:18

'הן לא הובא וגו‎ BEHOLD [THE BLOOD OF IT] WAS NOT BROUGHT [IN WITHIN THE HOLY PLACE] — for if it had been brought,then indeed was it your duty to burn it, as it is said (Leviticus 6:23) “Any sin-offering whereof any of the blood is brought [into the appointed tent, … shall not be eaten; it shall be burnt in the fire]” (Zevachim 101a; Pesachim 82a);

הן לא הובא את דמה אל הקדש פנימה, into the sanctuary; all sin offers whose blood is destined for the golden altar or dividing curtain must be burned as has been made clear in Leviticus 6,23. None of it must be eaten by the priests. However, the sin offering under discussion is one whose blood was sprinkled on the copper altar in the courtyard of the Tabernacle.

You should have. It does not mean they should eat it now, as the expression implies, since it was already burnt.

אכל תאכלו אתה YE SHOULD INDEED HAVE EATEN IT although you were Onanim,

כאשר צויתי AS I COMMANDED you in the case of the meal-offering (vv. 12, 13).