Okay, you need to make one important assumption when tackling this problem, which is you need to assume that HCl reacts with an excess
of sodium sulfite solution.
If this is the case, what can we say about the equilbrium, and how will we set up HH equation?
EDIT: It looks like you made it above:
I considered that the moles oh HCl are the same of NaHSO3.
That's good, what happens next?