Who was the first to notice that You have a financial problem? Was it the Manager or the HR?
You did the right thing by accepting the offer, Ur a loyal employee, U help Ur company when it is in need, but the problem is, if Ur company only noticed Ur financial problem when U submitted a resignition that could be a major light to Ur skill and service towards the company.
But this is a stupid thing to do, you accepting the offer and the company offering an increment when U have to departure, these is all stupidity.
Do not take the increment if U want to stay, but if U want a name tag, take the increment & stay. I would suggest that U leave if U need a career development, because money is not the only compensation, there are other resolutions and benefits in other companies.
Unless the increase can increase Ur savings