One of the little tricks I have discovered for removing creases is the "average vertices" command. You would need to first combine the right and left side, then it takes a little bit of guessing as far as which verticies to select to get the right effect, but it can save you a lot of time. Usually in this particular situation, I would choose the vertices only in the general vicinity of the seam, then average then and see what the effect is. It is somewhat tricky to get exactly what you want in each particular area, so it may work well in some areas and not in others. In an area like the nose you might need to re-edit the position and then average vertices again, but it is a good method that beats trying to manually get rid of a crease!