ぺったりclosely (sticking, clinging, etc.), tightly

塗(ぬりぐす)り薬()をペッタリと塗(ぬ)る。

The sentence seems to be incorrect or incomplete. The verb "nuriru" would mean to paint or to apply (like a cream or medicine) but it's not properly conjugated or used in the sentence. If you meant "塗り薬を塗る" it would translate to "apply the ointment." {closely (sticking, clinging, etc.), tightly}

驚(おどろ)いてペッタリと尻餅(しりもち)をつきました。

Surprised, I fell flat on my butt. {closely (sticking, clinging, etc.), tightly}

切手(きって)を封筒(ふうとう)にペッタリ貼(は)ってポストに入(い)れる。

Stick the stamp tightly on the envelope and put it in the mailbox. {closely (sticking, clinging, etc.), tightly}

スーツケースには複数(ふくすう)のステッカーがペッタリと貼(は)ってあります。

Multiple stickers are tightly stuck on the suitcase. {closely (sticking, clinging, etc.), tightly}

少(すこ)し前(まえ)までペッタリくっついてくれた子供(こども)が、今(いま)ではくっついてくれない。

The child who used to stick closely to me until a little while ago, doesn't cling to me anymore now. {closely (sticking, clinging, etc.), tightly}