。
I got bruises on both legs.
Literal
Both-legs [on-に] bruises [subject-が] formed-regrettably.
痣 (あざ, bruise/mark) is uncommon kanji. ができてしまいました chains ができる (to form/appear) + てしまう (regrettable completion) + ました (polite past). The speaker regrets that bruises appeared — an unintended, unwelcome result.