There is a short window of opportunity to undo a file action (move, rename, copy type) in Windows Explorer or folder windows using the Edit Menu (or pressing Ctrl Z). You would see undo rename as the option for example. Only the most recent file action will be un-doable, so it may be too late.
It appears that you had multiple files selected when you did the rename. When you have multiple selections Windows will rename them using the name you enter and the bracketed sequential numbers.