If using the English expression "no worries" as a way of responding to someone thanking you for something, Norwegian translations such as "bare hyggelig" or "ingen årsak" (or even "det var da så lite") would work well.
However, as you have grouped "no worries" together with "don't worry" and "it's fine" in your question, I suppose you might be looking for the Norwegian equivalent to "no worries" when used as a response to an apology, or as a reassuring reply to someone raising a problem of some sort. In that case, you would need to use some other translations in order for the response to make sense in Norwegian. Some examples:
A: I'm really sorry I won't be able to help you out on Thursday.
B: No worries / Don't worry / It's fine , I'll ask my brother instead.
A: Jeg beklager veldig at jeg ikke har mulighet til å hjelpe deg på torsdag.
ELLER: Jeg er veldig lei meg for at jeg ikke kan hjelpe deg på torsdag.
B Alt. 1: Ikke noe problem, jeg kan spørre broren min i stedet (ELLER: ..., jeg spør heller broren min.)
B Alt. 2: Ikke tenk på det, ...
B Alt. 3: Det går (helt) fint, ...
B Alt. 3: Det går bra, ...
B Alt. 4: Det ordner seg nok, ...
A: I would love to come with you to the party, but I've got nothing to wear!
B: No worries / Don't worry, I'll lend you something.
A: Jeg skulle gjerne ha blitt med dere på festen, men jeg har ikke noe å ha på meg!
B Alt. 1: Ikke noe problem, du kan låne noe av meg (/jeg kan låne deg noe).
B Alt 2: Ikke noe stress, ... (very casual)
B Alt 3: Det løser seg lett, ...
The most natural was to ask someone "How was your day?" in Norwegian — if referring to TODAY (i.e. the day that is yet not fully completed), and not to yesterday or some other day in the past — would be to alter the tense slightly in the translation, and ask "Hvordan har dagen din vært?" (lit.: "How has your day been?").
Good luck :)