If You got Your N950 via developer's program, You can use official means of repairing/replacing it (I'm not sure, if Nokia still proceed those).

If it's similar situation to one from few weeks before, when someone came here, asking about screen replacement for N950, that he got as birthday present from uncle working on Nokia's R&D - well, You know the answer.

BTW, of course, as other's have said, it's not dead pixel, but minor screen leakage.

/Estel