Does anyone know whats going on and the solution?

(PLEASE DON'T SAY, "YOU'RE OKAY", I'M LOOKING FOR ANSWERS NOT SUPPORT)

So, I used to be 50.8 kg which took me a good year to get down to from 80 kg. I was always 51.7 kg after the day then back to 50.8 kg in the following morning. I eat 1500 calories a day to maintain 50.8 kg. I usually have my cheat day's on Friday's, same meal EVERY Friday. Then came summer, I was fine for like the first 2-3 weeks. However, I had one cheat day on Friday, same meal I always had, and it spiked to 53 kg, "water weight no problem", is what I said. A few days of cardio and consuming 1500 calories, I went back on the scale and it said 52.6 kg. It's been 3 weeks and it's never gone fully down. I drank a lot of water, cardio, less food, more food, etc. The lowest I brought it down to was 51.7-52.6 (in that range). Did I really gain actual weight from ONE cheat meal? Does anyone know how to fix this? This has never happened to me?