"Do not worry about the distance."

Translation: Nie martwcie się o odległość.

[dorpderp]

Should "nie martw się o odległośći" also be correct? Any reason why or why not?

[Vengir]

Yes, it should be also correct. „Martw” is singular, while „martwcie” is plural. Many, if not all, plural imperatives are formed by adding -cie at the end of the singular form.

[Jack.Elliot]

yes

it could be both

thanks

[immery]

"nie martw się" is correct. but "odległości/odległość" has a spelling mistake, and odległości is plural

[WquDT]

It is " nie martw sie o + accusative noun" .

[karaluh]

"nie martw się odległością" should be accepted.

[Jellei]

OK, added.