IMO, the first is worse. It doesn't seem that memories of pain will actually hurt you, unless they come with effects other than just memory, like, for example, PTSD. And the pain may have been in the past, but just because you don't remember it doesn't mean it's the same as never having happened. The suffering is still important. Just like you'd actively avoid suffering in the future even though it hasn't happened yet, pain in the past is equally real and undesired.

And what type of torture does that?

Qafka! Welcome back! For me, it would be the latter because I think it would cause PTSD.

I have some questions … did this horrific pain in affect my physical well being in the long term? And also, is the memory of the pain traumatizing to my mental well being?

Pain implies that your body is somehow being physically damaged. The former sounds better, but taking that implication into account, it's actually worse.

Important to note that bad false memories can also be considered some sort of damage, but of a mental nature. So I consider your question as a trade-off between physical and mental damage.

The latter sounds far worse

I guess it depends on how we're defining worse - for me it's about the temporary suffering of having no memory after vs. the lasting memory of suffering, real or not...and in that sense it's the latter and it's not close