It won’t stay perfect, those will expand and contract at different rates, but if you want a cheap and quick fix, just get some caulk in roughly the same color. You could use joint compound as the other poster suggests, but caulk has some give, it’s likely to still separate again at some point, but you’ll have longer. The permanent solutions all kind of suck and/or are expensive, if you decide to try to reposition it and the issue recurs, I wouldn’t do it more than once.