ママの男が部下連れてやってきたわ。
こんな日にシフト入れちまったわ
The characters are two hostess talking in the back room. Host 1 points out mama's man bought subordinates to which host 2 points out she ended up placing her shift in a day like this.
What nuance does ちまった provide here? Is it mean to sound like a complain? Like "oops, of all days I hate pick this one?"