Got adhesive grime stuck on plastic back cover of my camera. Mild soap wipe didnt work. How do I remove?

The camera is a Nikon F80 SLR with a back cover that allows date printing. The cover is made of plastic probably some kind of thermoplastic. I have no idea how the sticky substance got onto the camera or what it is exactly (got there after my sis used the camera). It looks and feels like the sticky grime that some stickers leave on certain surfaces after you peel off the sticker. I've tried wiping it with mild soap solution but that wasn't very helpful. They only way I know of removing the substance is by slowly and painstakingly scraping it to the side and then pinching it off but it takes forever and no matter how hard I try there's always going to be some grime left over. Please help. Many thanks!