John Gill Commentary Leviticus 10:18

"Behold, the blood of it was not brought into the sanctuary within: ye should certainly have eaten it in the sanctuary, as I commanded." — Leviticus 10:18 (ASV)

Behold, the blood of it was not brought in within the holy
place
When that was the case, indeed, the flesh of the sin offering was not to be eaten, but burnt, see (Leviticus 6:30) but this was not the case now, and therefore its flesh should have been eaten, and not burnt:

you should indeed have eaten it in the holy [place], as I commanded ,
(Leviticus 6:26) .