There are two pertinent issues to address here. First, not all forms of research require consent since some data collection doesn't subject participants to any stress or other form of risk and some forms of data will not disclose identifying details of your subjects' behaviors, biomarkers, or other characteristics. In all cases, how far you are required to go in obtaining informed consent depends primarily upon how much 'risk' your participants were exposed to by agreeing to participate in your experiment. This includes 'risk' undertaken by participation and 'risk' they may be exposed to when the data becomes public in some form. If you are doing research within the US, for instance, you should have gone through an IRB process beforehand. When an IRB determines that there is some risk (even minimal) they will require a researcher to stipulate how that risk will be mitigated and may require the researcher to brief subjects about before or after the fact.
However, some forms of data and data collection pose no risk to your participants and can be exempted. If your data set includes no identifying information (including names, biomarkers, photographs, video, etc) then you may not actually have needed an ethics board (or IRB) clearance and there may be no issue with your advisor whatsoever. Online surveys, for instance, or observations of public behavior, do not require consent of any kind, and several other types of research which pose exceptionally low risk can proceed without much sign off. It is possible that obtaining verbal consent from your participants would satisfy your university, but I cannot say for sure. You will need to inquire at your university to figure out whom to consult about this. It will be different at each institution. Since you've indicated that you carried out an experiment on roughly 50 people, I'm guessing it's behavioral research you're conducting. The good news is that in many experimental studies, subjects are expected to be fully informed and give consent only after the experiment has been conducted. There is much precedent for this in psychology.
Second, your relationship with your advisor, while there are gray areas depending upon discipline and university, is not a boss-employee relationship when it comes to your own independent research. If you are getting credit for what you are doing, then you are the one who bears responsibility to make sure that what you're doing is ethical and well considered. I'd suggest that this isn't your advisor's responsibility unless it was clear that your were working on her/his behalf. However, if you and your advisor are having difficulty communicating about expectations and you're receiving little guidance on how to design and carry out research, I would suggest taking on an additional mentor, either in the form of a secondary advisor or graduate counselors at your university.