Brownout and brain damage?

Last night I was really congested because I've been sick with a cold. When I was in the shower I blew my nose, a lot, and repeatedly, to try to alleviate it. After a while, I got really dizzy and my vision blurred. I didn't blakout and eventually got back to normal, but I was wondering If episodes like this can cause even slight brain damage, brain cell death, or be in any way detrimental to memory or cognitive function. Ah, I really hope this doesn't seem funny, 'cause I've been (maybe obsessively) worried about how something like that could affect me and would like to get a good a good answer. I also don't wanna seem like a prick by worrying about this when other people suffer from much more serious issues, but, like I said, I might be obsessing.