Help! I've fallen and I can't get out of this cell

So, I don't know what exactly an "array" is, but apparently I have managed to create one while copying a row of cells from one workbook to another. 

I pasted my cells normally instead of pasting values, and now there's a formula present in the first pasted cell. It wouldn't be a problem except I accidentally clicked inside of the cell and edited part of that formula. Now i'm getting the "You cannot change part of an array" error. My cursor is literally trapped inside the cell. I can't even exit the sheet.

Save for rebooting, is there anything I can do?