decal distortion when resizing

I have created a 3d object in PS and imported as 3 obj files. when I attempt to import the image I want on the front plane of one of the obj elements it comes in far too small. when I try to resize it the image completely distorts as if magnetically pulled into the corners of the obj. the panel of the obj I am trying to apply the decal to is a flat star shape. the decal is an identically shaped png image. any suggestions gratefully received as this is driving me mental.