Oh holy cow, I am so sorry. :(
I feel you, I have made posts that have erupted into crappy 500 note behemoths of unpleasantness.
First, turn off anon asks for a bit. Don’t sweat the haters.
You can handle it one of 2 ways, IMHO:
1) If you really did say something not-so-great, that is okay! Everyone makes mistakes. Acknowledging your mistake is a good place to start. Even if you just came off badly or heck maybe people misunderstood you, just reblog your post once and clarify or apologize as you see fit.
Then let it go and don’t come back to it.
I don’t recommend deleting because everyone will see the reblogs and…well, I’m a big supporter of owning what you post, even if its not so great.
So yeah, clarify(or defend)/apologize/make a final statement on the subject & walk away.
Here is the other option:
2) Just walk away.
Just drop it and let it go. Make sure you have your notifications turned off & again, no anon asks. Just let it go and chalk it up as an experience that will help you in the future.
I know these arent really helpful but its just my personal way of dealing with stuff like that on tumblr. Trust me, I have done both.
Obviously this is based on the vagueness of your ask. It could change somewhat depending on what was said.