「、」。
Yoshiki is grumbling 'it's cold, I don't want to' through a crying face.
Literal
Yoshiki-kun [subject-が] 'cold [assertive-よ], dislike [assertive-よ]' [quotative-と] crying-face [at-で] is-grumbling.
A vivid child-scene in the present progressive. 泣きっ面 (なきっつら) is a compound for 'a crying face,' 'a face in the middle of crying' — the small っ in 泣きっ is an emphatic/intensifying pause. The compound often appears in the proverb 泣き面に蜂 ('a bee on a crying face' = when it rains it pours). ぶつぶつ言う is the standard collocation for 'grumble,' 'mutter,' 'complain under one's breath' — ぶつぶつ is a 擬態語 for the muttered, choppy sound of grumbling. The で on 泣きっ面で marks the manner or condition in which the grumbling is being done — 'grumbling with/in a crying face.'