It might be a good idea to have your primary care physician check out the site of the cyst just to make sure there’s no evidence of return.
If you’re only perspiring in the tailbone area, I wonder if that was possibly affected by the surgery? Did this extra perspiring start after the surgery? Although that lower back area is a pretty common place for perspiration.

Does it bother you from the perspective of “Why am I sweating there, is this abnormal” or is it from sweating hard enough to cause embarrassment?
If it’s embarrassment, I think you might appreciate this story and maybe it will help you out if it’s from worrying about butt-crack sweat. I can’t believe the timing on this in relation to seeing your post!
Our neighbors have teen boys. Very athletic and they naturally perspire a lot. The oldest just graduated high school and had to give the valedictorian speech. He was worried about getting up in front of everyone with ‘butt-crack’ perspiration showing on his pants if he stood up. His mom fixed him up with panty liners adhered to the Inside back of his skivvies. LOL. He freaked at first but then let her do it! It worked by absorbing excess sweat. No one knew!!! And, he hit her up for some extras to pack when he went off to the dorm. That’s a brave kid! 😅
Yep, as an 18 year old, that’s the last thing you want to be seen buying at a grocery store. But if it’s the embarrassment aspect of perspiring from your tailbone area, maybe ask your mom for some advice?