hi! i have been using Krita for a while now and today when i opened it the UI was massive! i haven't changed any setting anywhere and i don't know whats wrong

So, though you don't say so, I guess you're on Windows? Check your Windows Display Scaling setting in the Windows Settings app. If it's like 200 or higher, dial it down. In Krita, you can also disable the HiDPI setting.