I'm not sure, but the DC-10 has a similar strake on its nacelles, also on the inboard side I think. Maybe it produces a vortex to energise local airflow over the wing, or maybe it reduces the strength of an existing vortex, to reduce drag. The gap between engine nacelles, wing and fuselage can produce unexpected drag increases, in the form of a local 'choke point'.
I wouldn't want you to think that I know what I'm talking about though.......