I goofed and rejected a suggested edit, a vote that was actually directed at the previous edit that I was reviewing. As this is unfair to the user who posted the suggested edit in question, is there any way in which to change/cancel my reject?
No, you can't change your decision.
However, don't feel too bad about it. No one will scowl you for getting one wrong (That's why you need 3 reviewers anyway).