Hi - I put a border around my image and now I want to get rid of it but when I select it I can't find an eraser or tool to use

The attached image shows the Eraser Tool in Photoshop.  As a previous person mentioned, a screen capture would be most helpful.  Keep in mind that the Eraser Tool erases the pixels, meaning what is under the border will also be deleted.

If the size isn't important, you can crop off the border, or perhaps you can select the area with the border and rebuild the edge with a content-aware fill. Or you can return to the original image (because you always want to work on a copy, never on the original) and start over.

So many choices, but we are just making wild guesses until you share a screen shot with the Layers panel open and visible. Use the button outlined in orange:

Assuming it's not on a separate layer, a screen shot would help.