I dyed my hair blonde how long do I have to wait to put pink over the blonde?

You should be able to apply it right away. However, because you most likely still have some open cuticles from the blonding process, you may get some fast fading of your pink color. My suggestion to help slow this fading is this: After applying the pink color, allow to process the full time. Then, use a deep conditioner to help close the cuticle and make your hair smoother. A day or two later, use a clear semi permanent gloss over your hair to add shine and coat your hair to keep the pink color more secure. Don't wait too long between the blonde process and pink process because even a few days will give you some new growth to deal with.