Working with Adobe Photoshop extrusion in Dimension: adding original image

heres the thing... in 3D \ 4D the model is much more important than the image so you are generally best to start from there if its just a wafer thin but yes Photoshop can do this as well and I use that when the base is more complex

example

p.s, at certain camera angles a flat wafer just doesn't cut it... its now that I nomally break out Photoshop to build the model instead of starting from Dimension 1st

the steps depend on the shape of your image mate so a square is going to need less work than a spider

for mucky about your best option is to start playing with opacity maps

https://community.adobe.com/t5/dimension/how-to-create-custom-3d-model-and-import-as-obj/m-p/11084592#M3318

this is a simple box example but the point is you can apply the same workflow to make a hole or cut around a person and the key issue is pixels i.e, if your image is something like a person with blank pixels around where you cut them out then those missing pixels still count when you make them into a 3D model... this is normally where new players go wrong

it sounds like you made the error in Photoshop so your best option is to go back there to fix it

share the file if you need help