。
Don't keep butting in from the sidelines.
Literal
Side [locative-で] various thing [object-を] don't-say-[please give me-てくれ][emphatic-よ].
An irritated request. 脇で ('on the side, from the sidelines') refers to being nearby but not central to the action. いろいろ言う ('to say various things') = 'to make various comments, nitpick'. 言わないでくれよ combines the negative ないで form + benefactive くれ + emphatic よ — a rough plea 'don't do this for me!'. Characteristic of family/friend irritation.