Puppy biting older dog

We recently had a Golden Retriever/Husky puppy (Chip) fall into our lap after being rehomed several time and we LOVE him.

Our only concern is that he plays very rough with our older dog (Stella). Stella doesn't seem to mind much, but she has some loose skin around her neck and Chip bites her so hard when playing that the area has lost fur and caused her to bleed.

The problem is that because Stella doesn't seem to mind, Chip isn't learning to be more gentle, and when we try to correct, Stella thinks she is in trouble.

Do you guys have any advice on what to do?