I don't think anyone here can say if it will be a "huge problem" to tell them now. But, most likely, if you do not tell them now, it will be a "huger" problem if they find out on their own.
Let me add that you appear to be on the road to having the IRCC be paying close attention to your
bona fides. In March you were asking here about questionable reporting of your education and work experience. As
@YVR123 properly advised you then, you should always fill in the forms according to the truth. Not really a difficult concept.