this morning when i looked at it again, i frist thought it was gone, but after some usage, it came back.
taking a closer look, i saw, that the slcd foil(?) under the glass has bend a little bit, what seems to be the reason for this yellow stain. i think it might be a heat problem, since it was gone this morning, but came back after some usage.
i also think it might have to do with using navigation, since my nexus really gets hot while using that.
anyway i will bring it to the shop, but i'd like to know if there were others experiencing this..
here two pics attached (the stain can't be seen that good on a picture).