Okay, it's not the end of the world. Don't cry.
Make sure it's dry and then sit down in good light with a tiny pair of scissors and some tweezers. Grab a piece of the unwanted interfacing and dangle the project so that the weight of the project is pulling on the interfacing and stretching it out.
Hold it up to the light and start snipping around the edge with the scissors.
It will take some time, and you will need to go slowly to avoid snipping embroidery threads or the sweatshirt, but you can get rid of this.
When you have removed all that you can get to, there may be some spots that need covering over - just use the same color of embroidery thread and stitch over it by hand.