I am assuming that his blood tests were for IgG, not IgM, correct?
Were you also having intercourse with him when he got whitlow? Unprotected or protected?
It really isn’t possible to know with 100% certainty that he doesn’t have this genitally if you were also having intercourse at the same time BUT if it is only on his finger, then it is very likely that he will not contract HSV 2 genitally or orally in the future.
Terri