At one time I was in the drycleaning business, specializing in refinishing leathers. If the stain is glue coming through the material, it cannot be removed. In fact if any type of solvent is used to remove the stain, the glue will spread and worsen. Sanding with an abrasive block is an idea, but I wouldn't take a chance. I agree that the best and maybe the only option is to spray paint the area with a paint that is designed to cover vinyl or leather (is it vinyl, leather, or cloth?). If vinyl or leather, spraying would be the best option. If cloth, there are probably no options other than replacement in my opinion. Locating the correct color is not easy.
We had a similar problem on my 1962 Mercedes 220SEb in that the leather was all faded and stained on one door panel. We use SEM products for such issues. The maroon that we had was too dark and the dark red that we had was not even close. By careful blending (spraying one color over the other in light mists) we were able to get it to the point that it matched the rest of the car. We painted the entire door panel however, as felt certain that we would not be able to blend it in with the original. Attached picture shows the door of the '62 Mercedes SEb prior to our spraying as explained to above. Sorry no after pictures at this time.
Back to the glue problem. Last year I was installing a trunk lining material in my 1954 Buick and the spray glue that I used was too strong (was for carpet, not upholstery). I ruined the section (glue bled through the lightweight material) and I had to order 1 more yard of material at $85 per yard ,and sew in a replacement section. I then used 3M spary adhesive, which emits a finer mist and is not as active as the carpet spray cement. Even then I was very careful not to spray too much glue at once, allowing some time between coats. We were preparing the car for national judging and got into a last-minute crisis (almost). Attached picture shows the trunk after completion. The area that had to be replaced is shown directly above the fire extinguisher. The car received 400 points out of a possible 400 points at Charlotte last summer. I do all of my own trunk linings and carpets, some uphostery and door panels, but not convertible tops or head liners.
Fritz