As stated, conducting research on humans without prior ethical approval is a grave transgression. The work becomes unpublishable because no journal would touch it (as a matter of universal policy) and you are open to formal censure.
However, this depends on nuances of your country, institute/department and possible categorisation of your work. Not all human research is ethically equal, and this is why a supervisor's guidance is crucial. Their academic well-being should be on the line over the activities of their mentees, and yours failed to do their job, but that's a rant for another time.
What follows does ultimately hinge on supportive engagement of your supervisor, so it is doubly dismaying to hear what sounds like distancing noises from them. If they are jettisoning this very professionally hazardous mess on to you then I am sorry, and I wish I could say it was rare.
In UK Psychology departments provision is often made for "generalised" ethical approval based off the Principal Investigator (your supervisor), or prior approved research from which the present does not materially deviate in ethical terms. There might well be rules which say no, or only cursory further approval is required for a study which essentially extends a previously approved study, i.e. by deploying the same methods to study the same topic/cohort such that no new ethical considerations are raised. If your supervisor is lucky (these days), they might have wangled blanket ethical approval for a whole class of prospective experiments on this rough basis: same kinds of methods on the same wholly mundane participants for roughly the same ends. Some kind of special remit is also typically extended to final year undergraduate project students, given there are so many and their projects are often trivial recapitulations of wholly harmless designs reused yearly by the supervisor in this way. (Note that those are usually very strongly stipulated conditions of being able to go this quicker route, which still entails prior ethical approval just through a faster cut-down process, and a signed statement of taking responsibility from said supervisor).
Ultimately then, the slow and onerous ethics committee approval process will probably include allowances to make specified cases of especially low-risk research more expedient, and although the bounds of these are very tightly specified because of the gravity of ethical risk, many PIs are wont to exploit the letter of the law (academics are professional arguers after all). As I've said they typically do so for two reasons: to circumvent the sheer onerousness and slowness of the full approval process, or to retrospectively render disorganised and messily planned research ethically approved. I have seen these rules creatively interpreted in the service of either goal far more often than those writing such rules would like.
Your case might fall into the second category, and it should be clear here why the benevolence and alliance of your supervisor is key. I have seen supervisors protect their juniors (and their findings) from the mess that you are in, following similar disorganisation and poor mentorship, by finding a way to frame the research conducted as coming under the remit of previously granted ethical approval. Perhaps this rogue study can in fact be argued as a mere extension of a previously approved study. Perhaps this study's ethical ramifications are sufficiently trivial that it could fall under some aforementioned triviality type allowance. Significantly, all of this is meant to be obviated by the iron imperative to resolve any such approval ambiguity before conducting the research - but perhaps there are only one or two, non- or back-dated bits of paperwork that need be collected to bring the study back into defensible territory.
None of this is at all on the table unless the supervisor wants it to be however, and if they don't, the mere suggestion of this to them will be responded to as a grave professional hazard. It sounds unfortunately like your supervisor specifically might prefer what is now smeared on you, to remain smeared on you alone.
I saw this kind of thing happen as the not-unusual solution to a full approval process being too long for certain deadlines, valuable juniors (or their findings) being jeopardised by the kind of situation you've been allowed to get into, other forms of craven programme disorganisation, or combinations thereof. Is this whole thing very uncomfortable if not inappropriate? I invite you to read some other responses on this site regarding how much inappropriateness is forgiven, when it is not a mere junior in the firing line.