Let $S_1$, $S_2$ be homologous embedded 2-spheres
in a compact smooth 4-manifold. Under which additional
conditions they are smoothly isotopic? I am interested
in the state of the art picture when $S_i$ are
spheres with self-intersection -2 in a K3 surface.
However, any related information (for other
4-manifolds, and for extra assumptions on $S_i$,
such as Lagrangian or pseudoholomorphic) will be
also much appreciated.

I looked around and found many papers about
knotted 2-tori and Lagrangian 2-tori in symplectic
4-manifolds, but nothing about knotted 2-spheres.