This makes no sense. Even if you did have Covid (you probly didn't), I don't see a reason to regret getting the vaccine. You also don't know how severe it would have been had you not gotten the vaxine. It's possible it was Covid and the vaccine saved your life, or at least saved you a stay in ICU.
I have no regrets. I had a sore arm twice, and a bit of fever one night, and I still don't regret it. I won't regret it even if it somehow turns out that I got it for nothing, or even if I get a bad break through case. I calculated the risk vs reward and went for it, done deal. Regrets are dum.