The "blood brain barrier" is a chemical diffusion barrier, like a mesh (except it isn't a mesh) that blocks certain structures but not others. The vaccine components weren't supposed to go through but apparently some do. That's bad enough. However, a swab up your nose still has to go through bone to get to your brain. It is possible to erode those thin bones, say with chronic sinus infections, but the results aren't a lobotomy, they are meningitis. Meningitis shows up in the CSF

Couple of pictures here which show where the olfactory nerve endings are, the ones which covid screws up. Seems to me scraping around a lot with test swabs would also damage them. https://www.quora.com/Does-nasal-cavity-lead-to-the-brain

The prefrontal lobotomies done in the US generally involved sticking a thing like an ice pick through the bone behind the eyes. Nice picture several paragraphs down of a victim's skull. https://www.livescience.com/42199-lobotomy-definition.html There were a variety of other ways to accomplish this, a very sorry chapter in medicine. But a nasal swab won't do it.