That is the problem with Googling. You got yourself into panic mode now and it's very hard to think rationally.
No one here can tell you, you don't have brain cancer 100%. But, you don't have it probably around 99%. And what about that 1%, are you in that group? Well, that is where your rational mind should kick in and say, wait a minute, so many ppl have palinopsia and anxiety and I went to doctor and he said I am fine, so that means I am most likely fine.