I apologise for joking around. I'll be serious now.
I'm sorry for being so foolish. I'll be more serious from now on.
Please ignore my jokes. I'll be more serious from now on.
「ふざけてすみません、真面目にやります」= I apologise for joking around. I'll be serious now. / I'm sorry for being so foolish. I'll be more serious from now on. / Please ignore my jokes. I'll be more serious from now on.
ボキャブラリー
apologise, I'm sorry = 謝る、ごめんなさい、すみません
joking around, being foolish = ふざける
serious = 真面目
now, from now on = これから
ignore = 無視する、気にしない
joke = 冗談
Sorry I got a bit carried away there, I'll be serious now.
この場合、次のような言い方ができますよ。
ーSorry I got a bit carried away there, I'll be serious now.
「すみません、ちょっとふざけすぎました。これから真面目にやります」
to get carried away で「調子に乗る・悪ノリする」という意味です。
ご参考まで!