Depends ... in theory it could if you got a specific intention. An interface enforces a specific API an Object does not.
it can be overkill, but this is a design question, as such it does not matter if it's 1 or N it's -> do I want to make certain it looks this way.
If you just got one class and you are not certain it will remain that way -> probably you shouldn't add an interface at the moment.
If it's a core part and it has to be that way and some parts shouldn't change without noticing than you should add an interface.