Hey Shajee -
Yes welding would require a little bit of UV work. So lets check a few more things and see if we can’t get this problem fixed. You could try to edit the normals and tangents in your modeling program and have them flow correctly and then re-import your meshes and it should reduce the problem. Also check the normal map of your body and head and make sure that it is not set to SRGB, it shouldn’t be by default but its a good test.
You could also move the seam line so that it falls not at the neck but under the tank top straps which would hide any lighting problems on the skin from view, or add a scarf / choke collar over them seam.
Thank You
Eric Ketchum