warped logic board damaging sim card

I have just rebuilt an Iphone 3GS, replacing the back cover, front LCD and digitizer and battery (original fault was a damaged screen and a blown battery), but on re-assembling the phone I noticed the logic board was slightly warped. Now when I try and insert a sim card in the phone, it is difficult to slide the tray in and it is scoring a line down the sim card as it is inserted. Everything else working on the phone and so it seems a shame to just junk it, my question is this. Is there any way to try and flatten the board out again, my thought is with steam but is this likely to cause more damage?