Hey people, i was wondering if anybody could help me with layer styles

Basically i used to pen tool to draw a shape, i rasterised it and put an inner shadow on it using the layer styles, now how i could erase a corner of that shape without the inner shadow moving around the part i've just erased because i'm trying to blend it into the background

I hope you know what i mean, and thanks in advance for any suggestions on how i can fix this