This happens occasionally and does not mean there was an error. The drooping can be subtle and a cosmetic problem. It may be due to a small amount of diffusion. It will probably wear off within a week or so. If the eyelid drooping is severe and interfering with your vision, you should return to your injector to see if you need eye drops to reverse this.
The most common side effects of Dysport are: nose and throat irritation, headache, injection site pain, injection site skin reaction, upper respiratory tract infection, eyelid swelling, eyelid drooping, sinus inflammation, and nausea. Your symptoms are in line with the common side effects, so you should not worry. Wait for the side effects to subside.